Now for finding the number whose percent value is given, subtract this value from 100% (100% - 36.3% = 63.7%) and multiply the obtained percentage by the number that is placed at the top of the y-axis (in our example, 63.7% × 1 = 0.637). In brief, after opening the file and cropping the ROC curve ( Figure 3A and and3B), 3B), activate and drag the horizontal ruler for finding the sensitivity (in Figure 3C, this percentage is 36.3). The obtained percentage value is then multiplied by the number that is displaced on the top of the y-axis (9.7% × 400 = 38.8).įor receiver operating characteristic curves (ROC), which show the relationship between sensitivity (y-axis) and 1-specificity (x-axis) for every possible cut-off, both horizontal and vertical rulers should be activated. Then subtract the percentage value of the mean of the target group from the percentage value of top of the standard deviation/error (54.1% - 44.4% = 9.7%). Repeat this process again but this time drag down on thee mean value of the target group (in Figure 1F, this percentage value is 54.1). Finding the standard deviation or standard error of the mean values: Click on the horizontal ruler and drag down on top of the standard deviation/error of the mean to show a percentage value (in Figure 1G, this percentage value is 44.4). Now, for finding the number whose percent value is given, multiply the obtained percentage by the number that is placed at the top of the y-axis (in our example, 45.9% × 400 = 183.6).ħ. Then, this value is subtracted from 100%, which displays the percentage of the location you want (100% - 54.1% = 45.9%). Without releasing the mouse button, when the measurement line is in the location you want, a percentage value is shown alongside the size (in Figure 1F this percentage is 54.1). During dragging, a percentage of Y is shown, which displays the distance from the horizontal ruler the beginning of the y-axis is 100% and the top of the y-axis is 0%. Creating a horizontal measurement line and finding the required number: Click on the horizontal ruler and drag down on your chart. Choosing percent unit from context menu: Right click on the ruler → “ Percent” ( Figure 1E).Ħ. Activating rulers: " View" menu → " Rulers" ( Figure 1D).įor activating rulers, pressing Ctrl + R also appears a ruler along the top and along the left hand side of the Photoshop canvas.ĥ. This action is used to prevent further movement of the graph during the next process.Ĥ. Locking the layer: “ Layer” panel → “ Lock” ( Figure 1C). It should be noted that cropping the chart has to be done carefully and the frame of the chart, exactly from beginning to end of the “y-axis” which displays a value (in Figure 1B this value is 400), should be selected.ģ. Cropping the chart: “ Image” menu → “ Crop” → press “ Enter” to confirm the action ( Figure 1B).įor cropping, the rectangular marquee tool from the tool panel can also be used. A, opening or importing a file B, cropping a graph C, locking a graph D, activating rulers E, choosing percent unit from context menu F, creating a horizontal measurement line G, finding the standard deviation/standard error of mean values.Ģ. Here, we have described a simple method for extracting data from graphs using Adobe Photoshop.ĭata extraction from graphs using Adobe Photoshop. In these cases, extracting the data from published graphs is a reasonable alternative. Contacting the authors in order to retrieve the data may take a long time and is often not very fruitful, because the research may have been performed so far in the past. On the other hand, disregarding such data may result in publication bias when conducting a meta-analysis. In meta-analyses, extraction of numerical data from graphs is commonly required it is however a challenging issue. Graphs/figures are non-textual elements of the results section of a paper that present important messages of the research ( 5). In general, results obtained from such meta-analyses may provide a more accurate representation of the effect of a particular treatment for a disease compared to any single trial that contributed to the pooled analysis ( 2). Meta-analysis integrates the results of several independent studies to derive conclusions about that particular body of research ( 4). It is often impossible for readers to pinpoint and review all of the primary studies, therefore narrative reviews, meta-analyses, and systematic reviews are valuable resources of the summarized evidence on a particular topic ( 3). With such a huge number of publications, both clinicians and researchers need to choose the most worthwhile studies for providing complete and accurate answers to formulated questions ( 2). In biomedical sciences, there are currently > 24 million citations in the MEDLINE database alone ( 1). Science has become a highly specialized endeavor and the total number of published papers has dramatically increased in the last decades.
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