Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Graph”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,207 records · Page 67Linked to original sources
PubMed1995

Quantitative fluorescence method for continuous measurement of DNA hybridization kinetics using a fluorescent intercalator.

We present a quantitative fluorescence method for continuous measurement of DNA or RNA hybridization (including renaturation) kinetics using a fluorescent DNA intercalator. The method has high sensitivity and can be used with reaction volumes as small as 1 microliter and amounts of DNA around 1 ng. The method is based on the observations that (i) for the usual hybridization conditions, intercalators such as ethidium bromide bind (intercalate) to double-stranded DNA (dsDNA) but not single-stranded DNA or RNA and (ii) there is a large increase in fluorescence intensity when intercalators such as ethidium bromide bind to dsDNA. In this application, the intercalator can be considered as a quantitative indicator of dsDNA concentration. When a small amount of intercalator is added to a hybridizing solution, the fluorescence intensity of the intercalators increases with increase in dsDNA. The hybridization reaction can thus be monitored by continuously recording fluorescence intensity vs time. Because the amount of intercalator bound to dsDNA is not necessarily proportional to dsDNA concentration, the time-dependent fluorescence intensity graph is not identical to the kinetic graph [dsDNA] vs t. However, the fluorescence intensity vs time graph can easily be converted to the true [dsDNA] vs t graph by means of an experimental calibration graph of fluorescence intensity vs [dsDNA]. This calibration graph is obtained in a separate experiment using samples containing known amounts of dsDNA in the ethidium bromide buffer used in the kinetic measurement. We present results of experimental tests of the intercalator technique using ethidium bromide as an intercalator and DNA from Escherichia coli and lambda-phage and Poly(I)-Poly(C) RNA hybrids. These DNA and RNA samples have Cot1/2 values that cover a range of 10(6). Our experimental results show that (i) the kinetics of hybridization are not significantly perturbed by the intercalator at concentrations where no more than 10% of the binding sites on DNA or RNA hybrids are occupied, (ii) the kinetic graphs obtained by the intercalator fluorescence method and corrected with the calibration graph agree with kinetic graphs obtained by optical absorbance measurements at 260 nm, and (iii) the intercalator technique can be used in the different salt environments often used to increase the velocity of the hybridization reaction and at the hybridization temperatures (35-75 degrees C) normally used to minimize nonspecific hybridization.

Bacteriophage lambda↗
PubMed2005

Inferring meaningful pathways in weighted metabolic networks.

An approach is presented for computing meaningful pathways in the network of small molecule metabolism comprising the chemical reactions characterized in all organisms. The metabolic network is described as a weighted graph in which all the compounds are included, but each compound is assigned a weight equal to the number of reactions in which it participates. Path finding is performed in this graph by searching for one or more paths with lowest weight. Performance is evaluated systematically by computing paths between the first and last reactions in annotated metabolic pathways, and comparing the intermediate reactions in the computed pathways to those in the annotated ones. For the sake of comparison, paths are computed also in the un-weighted raw (all compounds and reactions) and filtered (highly connected pool metabolites removed) metabolic graphs, respectively. The correspondence between the computed and annotated pathways is very poor (<30%) in the raw graph; increasing to approximately 65% in the filtered graph; reaching approximately 85% in the weighted graph. Considering the best-matching path among the five lightest paths increases the correspondence to 92%, on average. We then show that the average distance between pairs of metabolites is significantly larger in the weighted graph than in the raw unfiltered graph, suggesting that the small-world properties previously reported for metabolic networks probably result from irrelevant shortcuts through pool metabolites. In addition, we provide evidence that the length of the shortest path in the weighted graph represents a valid measure of the "metabolic distance" between enzymes. We suggest that the success of our simplistic approach is rooted in the high degree of specificity of the reactions in metabolic pathways, presumably reflecting thermodynamic constraints operating in these pathways. We expect our approach to find useful applications in inferring metabolic pathways in newly sequenced genomes.

Amino Acids↗
PubMedDate not supplied

The signature molecular descriptor. 4. Canonizing molecules using extended valence sequences.

We present a new algorithm to canonize molecular graphs using the signature molecular descriptor introduced in the previous papers of this series. While developed specifically for molecular structures, the algorithm can be used for any graph and is not limited to acyclic graphs, planar graphs, bounded valence, or bounded genus graphs, for which polynomial time algorithms exist. The algorithm is tested with benzenoid hydrocarbons and a database of 126,705 organic compounds. The algorithm's performances are compared against Brendan Mc Kay's Nauty algorithm, which is believed to be the fastest graph canonization algorithm for general graphs, with five series of graphs each comprising up to 30,000 vertices: 2D meshes (pericondensed benzenoids), 3D cages (fullerenes and nanotubes), 3D meshes (crystal lattices), 4D cages, and power law graphs (protein and gene networks). The algorithm can be downloaded as an open source code at http://www.cs.sandia.gov/ approximately jfaulon/QSAR.

Journal Article↗
PubMedDate not supplied

Novel characterization of proteomics maps by sequential neighborhoods of protein spots.

We consider a characterization of proteomics maps based on an alternative kind of neighborhood graphs for the protein spots on 2-D gel. The novel approach considers for every protein spot only the nearest neighborhood consisting of protein spots of higher abundance. The approach has the simplicity and advantages of the recently introduced characterization of proteome maps based on considering the nearest neighborhoods of protein spots, but it also has important additional desirable computational features. The characterization of the nearest neighborhood graphs of 2-D gel proteomics maps is sensitive to the number of spots considered and may lead to changes in the degree of similarity of different maps when the number of points has been changed, thus imposing restrictions on the protocol used for comparison of maps. The novel approach presented in this work is less sensitive to the number of points used in the analysis because graphs are constructed in a stepwise process in which the role of more distant neighbors has been diminished by linking a new spot to the nearest spot that has been already part of the neighborhood graph. In this way a graph with N + 1 spots is obtained from the graph on N spots by adding a single new link, while in the case of the nearest neighborhood graphs adding a new spot introduces novel neighborhoods and generally results in a graph that may differ significantly from the neighborhood graph on N points.

Animals↗
PubMed1999

Model-based morphological segmentation and labeling of coronary angiograms.

A method for extraction and labeling of the coronary arterial tree (CAT) using minimal user supervision in single-view angiograms is proposed. The CAT structural description (skeleton and borders) is produced, along with quantitative information for the artery dimensions and assignment of coded labels, based on a given coronary artery model represented by a graph. The stages of the method are: 1) CAT tracking and detection; 2) artery skeleton and border estimation; 3) feature graph creation; and iv) artery labeling by graph matching. The approximate CAT centerline and borders are extracted by recursive tracking based on circular template analysis. The accurate skeleton and borders of each CAT segment are computed, based on morphological homotopy modification and watershed transform. The approximate centerline and borders are used for constructing the artery segment enclosing area (ASEA), where the defined skeleton and border curves are considered as markers. Using the marked ASEA, an artery gradient image is constructed where all the ASEA pixels (except the skeleton ones) are assigned the gradient magnitude of the original image. The artery gradient image markers are imposed as its unique regional minima by the homotopy modification method, the watershed transform is used for extracting the artery segment borders, and the feature graph is updated. Finally, given the created feature graph and the known model graph, a graph matching algorithm assigns the appropriate labels to the extracted CAT using weighted maximal cliques on the association graph corresponding to the two given graphs. Experimental results using clinical digitized coronary angiograms are presented.

Algorithms↗
PubMed2006

Evaluation of clustering algorithms for protein-protein interaction networks.

BACKGROUND: Protein interactions are crucial components of all cellular processes. Recently, high-throughput methods have been developed to obtain a global description of the interactome (the whole network of protein interactions for a given organism). In 2002, the yeast interactome was estimated to contain up to 80,000 potential interactions. This estimate is based on the integration of data sets obtained by various methods (mass spectrometry, two-hybrid methods, genetic studies). High-throughput methods are known, however, to yield a non-negligible rate of false positives, and to miss a fraction of existing interactions. The interactome can be represented as a graph where nodes correspond with proteins and edges with pairwise interactions. In recent years clustering methods have been developed and applied in order to extract relevant modules from such graphs. These algorithms require the specification of parameters that may drastically affect the results. In this paper we present a comparative assessment of four algorithms: Markov Clustering (MCL), Restricted Neighborhood Search Clustering (RNSC), Super Paramagnetic Clustering (SPC), and Molecular Complex Detection (MCODE). RESULTS: A test graph was built on the basis of 220 complexes annotated in the MIPS database. To evaluate the robustness to false positives and false negatives, we derived 41 altered graphs by randomly removing edges from or adding edges to the test graph in various proportions. Each clustering algorithm was applied to these graphs with various parameter settings, and the clusters were compared with the annotated complexes. We analyzed the sensitivity of the algorithms to the parameters and determined their optimal parameter values. We also evaluated their robustness to alterations of the test graph. We then applied the four algorithms to six graphs obtained from high-throughput experiments and compared the resulting clusters with the annotated complexes. CONCLUSION: This analysis shows that MCL is remarkably robust to graph alterations. In the tests of robustness, RNSC is more sensitive to edge deletion but less sensitive to the use of suboptimal parameter values. The other two algorithms are clearly weaker under most conditions. The analysis of high-throughput data supports the superiority of MCL for the extraction of complexes from interaction networks.

Algorithms↗
PubMed2003

Protein evolution within a structural space.

Understanding of the evolutionary origins of protein structures represents a key component of the understanding of molecular evolution as a whole. Here we seek to elucidate how the features of an underlying protein structural "space" might impact protein structural evolution. We approach this question using lattice polymers as a completely characterized model of this space. We develop a measure of structural comparison of lattice structures that is analogous to the one used to understand structural similarities between real proteins. We use this measure of structural relatedness to create a graph of lattice structures and compare this graph (in which nodes are lattice structures and edges are defined using structural similarity) to the graph obtained for real protein structures. We find that the graph obtained from all compact lattice structures exhibits a distribution of structural neighbors per node consistent with a random graph. We also find that subgraphs of 3500 nodes chosen either at random or according to physical constraints also represent random graphs. We develop a divergent evolution model based on the lattice space which produces graphs that, within certain parameter regimes, recapitulate the scale-free behavior observed in similar graphs of real protein structures.

Amino Acid Sequence↗
PubMed2000

Patterns of palmar skin temperature alterations during transthoracic endoscopic T2 sympathectomy for palmar hyperhidrosis.

Transthoracic endoscopic T2 sympathectomy has been widely applied to the treatment of a variety of sympathetically mediated disorders. Palmar hyperhidrosis is probably the most common indication for thoracic sympathectomy, especially in certain subtropical areas. Which sympathetic ganglion is to be ablated and how extensive such ablation is enough to eliminate palm sweating are two important issues. Intraoperative monitoring of palmar skin temperature (PST) is the most frequently used method for assessing the accuracy as well as adequacy of ablation of the target sympathetic ganglia. With continuous monitoring of bilateral PST during the operative course of T2 sympathectomy, it was possible to depict the alterations of bilateral PST in response to specific surgical procedures in a real-time manner. For each case, a PST graph was obtained, which represented the graphical expression of intraoperatively recorded bilateral PST data plotted against time. The PST graphs of 93 consecutive cases were analysed. Three types of PST graphs existed, reflecting different responses of bilateral PST to different surgical procedures during the operation. In Type I PST graph pattern, found in 58 cases, skin incision and intercostal muscle dissection caused dramatic bilateral PST drop; and unilateral T2 sympathectomy induced synchronous bilateral PST elevation. Twenty-four cases demonstrated Type II PST graph pattern, in which unilateral T2 sympathectomy caused only ipsilateral PST elevation, although the PST-depressing effect of skin incision and muscle dissection was as significant as in Type I graph pattern. In the 11 cases who showed Type III PST graph pattern, neither skin incision nor T2 sympathectomy induced any apparent changes of PST on either side, giving rise to two rather flat PST curves on the PST graphs. These findings implicate that reciprocal interactions between bilateral sympathetic activities exist in the majority of cases, and that crossover sympathetic modulation may play a role in the neural control of the sudomotor and vasomotor activities of the palms. This study also provides information regarding how PST would possibly change following specific surgical procedures during transthoracic endoscopic T2 sympathectomy, which may be of importance to those who use intraoperative PST monitoring as a guide in determining whether or not the correct sympathetic ganglia are ablated for adequate sympathetic denervation of the palms.

Adolescent↗
PubMedDate not supplied

Visualization tools for blind people using multiple modalities.

PURPOSE: There are many problems when blind people need to access visualizations such as graphs and tables. Current speech or raised-paper technology does not provide a good solution. Our approach is to use non-speech sounds and haptics to allow a richer and more flexible form of access to graphs and tables. METHOD: Two experiments are reported that test out designs for both sound and haptic graph solutions. In the audio case a standard speech interface is compared to one with non-speech sounds added. The haptic experiment compares two different graph designs to see which was the most effective. RESULTS: Our results for the sound graphs showed a significant decrease in subjective workload, reduced time taken to complete tasks and reduced errors as compared to a standard speech interface. For the haptic graphs reductions in workload and some of the problems that can occur when using such graphs are shown. CONCLUSIONS: Using non-speech sound and haptics can significantly improve interaction with visualizations such as graphs. This multimodal approach makes the most of the senses our users have to provide access to information in more flexible ways.

Blindness↗
PubMed1984

Peak flow rate records in surveys: reproducibility of observers' reports.

Records of peak expiratory flow rate (PEFR), commonly used in hospital in the management of asthma, have not been evaluated as a method of identifying cases of asthma in population surveys. Four observers were asked to report on whether asthma was present or absent in 61 graphs of PEFR recorded two hourly for four weeks during surveys of working population. Agreement within individual observers was measured using a subset of 29 graphs which had been copied and distributed at random among the set of 61; agreement was good, from 90% in one observer to 100% in two. Agreement between observers was measured on the basis of all 61 graphs. Agreement occurred between all four observers in 69% of graphs, between at least three out of four in 97%, and, when pairs of observers were examined, between 72% and 93% of graphs. Graphs assessed as showing asthma demonstrated more within day PEFR variability (expressed as the number of days in which the difference between maximum and minimum readings was at least 15%) than graphs assessed as not showing asthma. Some graphs with little within day variability were assessed as showing asthma, apparently because they demonstrated between day PEFR variability.

Asthma↗
PubMedDate not supplied

[Factors which affect long-term patency in femoro-popliteal bypass].

INTRODUCTION: The aim of this study was to investigate how "run off", diabetes, cigarette smoking and early reinterventions influence long-term patency of the "reversed" and "in situ" femoro-popliteal (F-P) bypass grafts. PATIENTS AND METHODS: The study included 1991 patients with "reversed" F-P and 99 patients with "in situ" F-P bypass grafts operated on between 1988 and 1994. There were 153 (80.10%) male and 38 (19.90%) female patients in the group with "reversed" bypass and in the group with "in situ" bypass there were 78 (78.8%) male and 21 (21.2%) female patients. The average age of all patients was 59.04 (27-80) years. Eighty five (44.5%) patients in the group with "reversed" F-P bypass had diabetes mellitus and 43 (43.4%) in the group with "in situ" bypass. One hundred and fifty two (79.68%) patients in the group with "reversed" bypass were cigarette smokers and 80 (80.8%) in the group with "in situ" bypass. In Table 1 patients according to Fontain's classification of occlusive arterial disease are presented. On the basis of angiographic examination all patients were divided into four groups (with patent all 3 crural arteries, with patent 2 crural arteries, with patent one crural artery and without patent crural arteries) (Table 2). All patients were controlled using physical and Doppler ultrasonographic examinations immediately after the operation; after 1, 3, 6 months and then every year postoperativelly. In cases with suspected graft occlusion or any other complication, control angiography has also been carried out. Statistical analysis of the results was performed using chi 2 and Fisher's test. RESULTS: The patients were followed-up from 3 to 10 years. In cases with patent all 3 crural arteries there was no significant difference in long-term patency between "reversed" and "in situ" bypasses (Fisher's test, P = 0.66; p > 0.05) (Graph 1). In cases with patent two crural arteries, there was no significant difference between groups with "reversed" and "in situ" bypasses chi 2 = 0.25, p > 0.05) (Graph 2). The long-term patency was significantly better in the group with "in situ" bypass if only one crural artery was patent (chi 2 = 4.96, p < 0.05) (Graph 3). In cases with occluded all three crural arteries there was no significant difference in long-term patency between the two examined groups (Fisher's test, P = 0.29; p > 0.05) (Graph 4). There was no significant difference between groups with "reversed" and "in situ" bypasses in patients with diabetes mellitus (chi 2 = 0.01; p > 0.05) (Graph 5). There was also no statistically significant difference between the two examined groups regarding the preoperative cigarette smoking (chi 2 = 0.94; p > 0.05) (Graph 6). However, in both groups postoperative cigarette smoking showed a statistically significant decrease in long-term patency (chi 2 = 66.71; p < 0.01) (Graph 7). The early REDO operations statistically significantly decreased long-term patency in both groups (chi 2 = 34.89; p < 0.01) (Graph 8). The late graft occlusions were found in 60 patients with "reversed" and 23 patients with "in situ" F-P bypasses. Table 3 shows causes of late graft occlusions. CONCLUSION: In some cases with pure "run off" "in situ" bypass technique showed better long-term patency. We preferred this technique when "run off" was pure, when diameter of the saphenous vein was small, and when bypass was "long". Diabetes mellitus had no significant influence on long-term graft patency in both groups, as well as regarding preoperative cigarette smoking. However, postoperative cigarette smoking and early REDO operations, statistically significant by decreased long-term graft patency in both groups. The reason was that cigarette smoking was not permitted postoperatively, while in cases with early reinterventions physical screening and ultrasonographic examinations were necessary.

Adult↗
PubMedDate not supplied

Spectral moments of phenylenes.

In a series of publications Estrada (Estrada, E. J. Chem. Inf. Comput. Sci. 1996, 36, 844-849; 1997 37, 320-328; 1998, 38, 23-27) employed spectral moments of line graphs in QSPR and QSAR relationship studies of various classes of compounds. A recent paper (Marković, S.; Gutman, I. J. Chem. Inf Comput. Sci. 1999, 39, 289-293) reported that in QSPR and QSAR investigations of benzenoid hydrocarbons based on linear combination of spectral moments, it made no difference whether one used spectral moments of the molecular graph or those of the line graph. In the present work spectral moments of molecular graphs (Mk) and line graphs (muk) of phenylenes are considered. The first few Mk's and muk'S of phenylenes are dependent on identical structural parameters. It is proved that the two sets of moments of phenylenes are linearly dependent. It is also shown that in the case of the heat of formation of phenylenes there is no advantage in using lower spectral moments of line graphs instead of lower spectral moments of molecular graphs. In this way the redundancy observed in the case of benzenoid hydrocarbons is also shown to exist in the class of phenylenes.

Journal Article↗
PubMed2003

Duplication models for biological networks.

Are biological networks different from other large complex networks? Both large biological and nonbiological networks exhibit power-law graphs (number of nodes with degree k, N(k) approximately k(-beta)), yet the exponents, beta, fall into different ranges. This may be because duplication of the information in the genome is a dominant evolutionary force in shaping biological networks (like gene regulatory networks and protein-protein interaction networks) and is fundamentally different from the mechanisms thought to dominate the growth of most nonbiological networks (such as the Internet). The preferential choice models used for nonbiological networks like web graphs can only produce power-law graphs with exponents greater than 2. We use combinatorial probabilistic methods to examine the evolution of graphs by node duplication processes and derive exact analytical relationships between the exponent of the power law and the parameters of the model. Both full duplication of nodes (with all their connections) as well as partial duplication (with only some connections) are analyzed. We demonstrate that partial duplication can produce power-law graphs with exponents less than 2, consistent with current data on biological networks. The power-law exponent for large graphs depends only on the growth process, not on the starting graph.

Internet↗
PubMed2006

Ring structures and mean first passage time in networks.

In this paper we address the problem of the calculation of the mean first passage time on generic graphs. We focus in particular on the mean first passage time on a node for a random walker starting from a generic, unknown, node x. We introduce an approximate scheme of calculation which maps the original process in a Markov process in the space of the so-called rings, described by a transition matrix of size O(ln N/ln (k) x ln N/ln (k)), where is the size of the graph and (k) the average degree in the graph. In this way one has a drastic reduction of degrees of freedom with respect to the size of the transition matrix of the original process, corresponding to an extremely low computational cost. We first apply the method to the Erdös-Renyi random graphs for which the method allows for almost perfect agreement with numerical simulations. Then we extend the approach to the Barabási-Albert graph, as an example of scale-free graph, for which one obtains excellent results. Finally we test the method with two real-world graphs, Internet and a network of the brain, for which we obtain accurate results.

Cell Physiological Phenomena↗
PubMedDate not supplied

UMLS-based conceptual queries to biomedical information databases: an overview of the project ARIANE. Unified Medical Language System.

OBJECTIVE: The aim of the project ARIANE is to model and implement seamless, natural, and easy-to-use interfaces with various kinds of heterogeneous biomedical information databases. DESIGN: A conceptual model of some of the Unified Medical Language System (UMLS) knowledge sources has been developed to help end users to query information databases. A query is represented by a conceptual graph that translates the deep structure of an end-user's interest in a topic. A computational model exploits this conceptual model to build a query interactively represented as query graph. A query graph is then matched to the data graph built with data issued from each record of a database by means of a pattern-matching (projection) rule that applies to conceptual graphs. RESULTS: Prototypes have been implemented to test the feasibility of the model with different kinds of information databases. Three cases are studied: 1) information in records is structured according to the UMLS knowledge sources; 2) information is able to be structured without error in the frame of the UMLS knowledge; 3) information cannot be structured. In each case the pattern-matching is processed by the projection rule according to the structure of information that has been implemented in the databases. CONCLUSION: The conceptual graphs theory provides with a homogeneous and powerful formalism able to represent both concepts, instances of concepts in medical contexts, and associations by means of relationships, and to represent data at different levels of details. The conceptual-graphs formalism allows powerful capabilities to operate a semantic integration of information databases using the UMLS knowledge sources.

Databases as Topic↗
PubMedDate not supplied

Comparison of vector and conventional bioelectrical impedance analysis in the optimal dry weight prescription in hemodialysis.

BACKGROUND: Dry weight prescription is commonly based on symptoms induced by inappropriate fluid removal by hemodialysis (HD). Aim of this study was to compare the assessment of volume status by conventional bioelectrical impedance analysis (BIA) and the resistance-reactance (RXc) graph method in HD patients achieving their target dry weight determined on clinical criteria. METHODS: We studied 39 HD patients (23 males and 16 females, mean age 52 +/- 17 years, dialytic age 41.2 +/- 37 months). Dry weight, prescribed according to the standard clinical criteria, was constantly achieved in the last 3 months. Patients symptom-free over the last 3 months were defined as asymptomatic. Patients with either muscular cramps or hypotensive episodes were defined as symptomatic. Thirty-three healthy volunteers (11 males, 22 females, mean age 50 +/- 11 years) constituted the control group. Standard, single frequency (50 kHz), tetrapolar, BIA measurements were obtained in controls, and in patients before, every 60 min, and 30 min after one HD session. Total body water (TBW), and extracellular water (ECW) were calculated using conventional BIA regression equations. In both groups, tissue hydration was also assessed by the RXc graph method. RESULTS: On the basis of 95% tolerance interval (mean +/- 2 SD) for the ECW (%) calculated in healthy subjects (ECW = 35-44%), HD patients were divided into 3 groups according to their post-HD ECW: 72% normohydrated with ECW 35-44%, 10% overhydrated with ECW >44%, and 18% underhydrated with ECW <35%. Patients were also classified into 3 categories according to the RXc graph method: 38% normohydrated with vectors within the reference 75% tolerance ellipse, 0% overhydrated with short vectors below the lower pole of the 75% tolerance ellipse, and 62% underhydrated with long vectors above the upper pole of the 75% tolerance ellipse. The progressive removal of body fluid during HD treatment was associated with a progressive increase in both impedance vector components, R and Xc. Eleven of thirty-nine patients (28%) were symptomatic during HD treatment in the last 3 months. The majority of these (73%) were classified as normohydrated according to ECW estimates, while 9 and 18% were classified as over- and underhydrated, respectively. This frequency distribution was significantly different from that obtained with the RXc graph method (chi(2) = 6.9, p = 0.03) where the majority (73%) were classified as underhydrated, while 0 and 27% were classified as over- and normohydrated, respectively. The frequency distribution of the 28 asymptomatic patients also significantly differed between conventional BIA and RXc graph hydration categories (chi(2) = 10.8, p = 0.005), since 11, 71 and 18% vs. 0, 43 and 57% of patients were classified as over-, normo-, and underhydrated, respectively. CONCLUSIONS: The classification of volume status based on conventional BIA was insensitive to either clinical situation (presence or absence of symptoms). In contrast, the classification based on the RXc graph was consistent with the clinical course in symptomatic patients (73% dehydrated, and 27% normohydrated), while it did not reflect the clinical course in asymptomatic patients, 57% of whom were classified as (already) underhydrated. A longitudinal study will establish the clinical usefulness of RXc graph indications in asymptomatic patients.

Adult↗
PubMed1992

Judgments of change and proportion in graphical perception.

Subjects judged change and proportion when viewing graphs in two experiments. Change was judged more quickly and accurately with line and bar graphs than with pie charts or tiered bar graphs, and this difference was larger when the rate of change was smaller. Without a graduated scale, proportion was judged more quickly and accurately with pie charts and divided bar graphs than with line or bar graphs. Perception is direct when it requires simpler or fewer mental operations; we propose that perception of change is direct with line and bar graphs, whereas perception of proportion is direct with pie charts and divided bar graphs. The results are also consistent with the proximity compatibility principle. Suggestions for improving the design of graphical displays are given.

Adult↗
PubMed2000

Statistical software for microcomputers: SigmaPlot 2000 and SigmaStat2

I cannot see any advantages for SigmaStat. SigmaPlot does indeed have many excellent features and any psychologist could feel proud of many of the graphs it produces (not the box plots). As to the competition, JMP-IN produces a similar rage of graphs (and a rotating 3D plot for factor analysis), but has much less flexibility about appearance in terms of colours, fills and other features of graph elements. It can also be difficult to make different graphs the same size appear neatly on the page. STATVIEW produces less graph forms, and does not perform the non-linear regression, but has similar excellent control of the colour, form and sizing of different graph elements. Both STATIVEW and JMP-IN have well implemented 'by variable' facilities and produce graphs well linked to their associated statistical analyses. SigmaPlot wins on the flexibility of its error bars. However, EXCEL and other spreadsheets are also well worth considering, as they produce the same range of graphics and are equally flexible over error bars. An experimenter would have to be very sure that the slight advantages in flexibility of presentation from SigmaPlot outweighed the hassle of having to totally re-organize their data.

Journal Article↗