Save marked point on plot

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Anton Vernytsky
Anton Vernytsky on 12 Mar 2022
Edited: Scott MacKenzie on 12 Mar 2022
Hello,
I would like to save the the x and y values of the marked point on the plot.
Can someone explain me please how to write a code or what functions can i use.
Thank you !

Accepted Answer

Scott MacKenzie
Scott MacKenzie on 12 Mar 2022
Edited: Scott MacKenzie on 12 Mar 2022
OK, this seems to to work. The x-y coordinates of the marked points are output to the command window (along with the figure number). For brevity, I'm just showing the result for the 1st data set.
format shortg
xlsdata=xlsread('temp.xlsx'); % this is the data in your ForDataMining.xlsx file
Wavelength=xlsdata(2:2152);
for i=1:1 % first data set only, adjust as desired
reflection = xlsdata(2:2152,i+1);
lmin = islocalmin(reflection,"MinProminence",0.01,"MinSeparation",100);
% get x-y coordinates of minima
x = Wavelength(lmin)';
y = reflection(lmin);
figNumber = repmat(i, numel(x), 1);
[figNumber x y] % output in command window (include figure number)
figure(i) % put figure statement here
plot(Wavelength,reflection,Wavelength(lmin),reflection(lmin),'ro')
title('Relative Reflectance-Wavelength')
xlabel('Wavelength[nm]')
ylabel('Relative Reflectance')
grid on
grid minor
end
ans = 7×3
1.0e+00 * 1 447 0.83857 1 1435 0.90312 1 1754 0.97845 1 1928 0.75198 1 2157 0.94879 1 2339 0.55042 1 2482 0.9139
  2 Comments
Scott MacKenzie
Scott MacKenzie on 12 Mar 2022
@Anton Vernytsky you're welcome. Glad to help.

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More Answers (1)

Scott MacKenzie
Scott MacKenzie on 12 Mar 2022
Edited: Scott MacKenzie on 12 Mar 2022
Since you haven't provided any data or code, this is a rough answer only:
[pks, locn] = findpeaks(-y, 'MinPeakProminence', 0.1);
Using -y will give you the valleys, which is what you are after. You'll need to play with the peak prominence value to the get the valleys you want and exclude those you don't want. Then, you need to take the negative of pks to get the actual y values of the valleys. You can use locn to retrieve the corresponding x values.
  4 Comments
Scott MacKenzie
Scott MacKenzie on 12 Mar 2022
OK,thanks. I posted a solution as a separate answer.

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