Extract Data From a Plot

Posted by Shaw, Matthew on Dec 09, 2016; 12:55am
URL: http://imagej.273.s1.nabble.com/Extract-Data-From-a-Plot-tp5017731.html

Hello,
I need help extracting data from a plot.  I found a very similar question
in the ImageJ archives:
https://list.nih.gov/cgi-bin/wa.exe?A2=IMAGEJ;b522272.1502

However, the ImageJ plugin: Figure_Calibration requires the user to pick a
few points from the ROI.  My goal is to have ImageJ return a robust set of
coordinates automatically.
I am specifically interested in getting pump curve data from manufacturer’s
published plots.  The particular solution will allow users to:

   1. Apply scaling to the ROI using Figure_Calibration.
   2. Set the threshold to distinguish a particular pump curve from the
   background.
   3. Use the wand tool to trace a particular curve.
   4. Reduce the pixels that represent a curve to a set of data points
   following the median width of pixel distribution.

As an example see the attached TIFF and Excel files, follow the 8” impeller
curve.  The data below was created using the Figure_Calibration plugin with
10 points selected with Multipoint tool.  The particular pump curve looks
very similar to the Figure_Calibration Tutorial here:
http://lukemiller.org/index.php/2011/09/digitizing-data-
from-old-figures-with-imagej/

Ultimately, the new plugin would allow users to obtain a General Solution
of the plot surface.  The general plugin would allow users to “read” the
domed surface plot from the efficiency contours, and create (or
interpolate) slice segments through the efficiency dome for any possible
pump curve (say 8.125 inches).

Does this plugin already exist for ImageJ?  I have seen references to two
programs that supposedly do similar things:
http://markummitchell.github.io/engauge-digitizer/
https://www.mathworks.com/matlabcentral/fileexchange/7173-grabit

I do not have administrative rights to use Engauge Digitizer, and I do not
have a MATLAB license for GRABIT.

Thank you for any help.
Sincerely,
-Matt Shaw

Mechanical Engineer,
U.S. Bureau of Reclamation

  Area Mean Min Max X Y
1 0 86 86 86 8.511 61.517
2 0 55 55 55 100 60.674
3 0 63 63 63 200 60.112
4 0 72 72 72 327.66 58.989
5 0 52 52 52 438.298 56.461
6 0 80 80 80 529.787 52.528
7 0 71 71 71 591.489 49.157
8 0 92 92 92 674.468 43.539
9 0 82 82 82 742.553 38.483
10 0 77 77 77 834.043 31.18

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