dear all,
i am doing a Meta analysis and facing a problem regarding the studies that does not include the results in a table form .some papers are showing the numerical values of results on graphs only which is not clear and mention only in results section the significant difference.
how can you extract these data for your analysis?
best.
Dalia
When you need to extract data from graphs, yes, you can contact the corresponding author and ask him/her for the numbers you need. However, 99% of the time, I have to resort to extracting numbers from the figures using an image analysis program. I use ImageJ (https://imagej.nih.gov/ij/), which is free and easy to use. If you have a PDF of the article, take a snapshot of the figure of interest. Convert the snapshot to an image file format (e.g., jpg, tif) and open in ImageJ. Measure the height of the bar (or whatever you are interested in) in pixels and then compare to the height in pixels of a known distance (e.g., length of y-axis).
Dear Dalia Yousif
These Youtube videos could be very helpful for your question:
https://www.youtube.com/watch?v=VHsbUHOk3is
https://www.youtube.com/watch?v=kswUZQ7Ep1M
https://www.youtube.com/watch?v=uemXMFvCfWM
When you need to extract data from graphs, yes, you can contact the corresponding author and ask him/her for the numbers you need. However, 99% of the time, I have to resort to extracting numbers from the figures using an image analysis program. I use ImageJ (https://imagej.nih.gov/ij/), which is free and easy to use. If you have a PDF of the article, take a snapshot of the figure of interest. Convert the snapshot to an image file format (e.g., jpg, tif) and open in ImageJ. Measure the height of the bar (or whatever you are interested in) in pixels and then compare to the height in pixels of a known distance (e.g., length of y-axis).
Hi Gordon - can you pls show us, using screenshots, how to do extract these numbers as I could not manage to do this? Krisnna.
Its better to contact an author always if you are unsure/confuse about data.
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