how to extract large number of data points from 2D plot

I want to extract large number of data points, like 30000 data ponits or more from 2d plot. Is it possible in matlab ?How to do it ?. These points will be used for other purpose but not for plotting. Thats why want large number of data points .

Answer 1

[Adam Danz]

If you can reproduce the figure, just save the coordinates in addition to plotting them,

plot(x,y,'o')
save('coordinates.mat','x','y')

If you only have the .fig file and need to extract the coordinates, open the file so it's the current figure,

fig = gcf();
ax = gca(fig); 
chil = ax.Children; 
x = get(chil,'XData');
y = get(chil,'YData');
z = get(chil,'ZData');

x,y,z, will be vectors if only 1 set of data are plotted on the axes. If more than 1 object is plotted, x,y,z will be a n*1 cell array for n objects.

Answer 2

[Ameer Hamza]

If instead of a fig file, you have an image, you can use this package to extract the data points: https://www.mathworks.com/matlabcentral/fileexchange/7173-grabit

[Aiden James]

Thank you sir. But can I extract large number of data points, like 30000 data ponits using above methods

[Ameer Hamza]

Can you show the image?

[Adam Danz]

Have you tried Ameer's suggestion? If you're pulling that fig from a pdf or some other resource that you can zoom into, you'll get better results by making the image larger and increasing its resolution.

[Aiden James]

Yes, I have tried it. But it is difficult to get large number of data points manually. Is there any command to get large number of data points, in which we can put no. of data points that points that we want.

[Adam Danz]

I haven't used that function but if it doesn't allow the user to specify the sampling rate, you can certainly interpolate the values it extracts.

Answer 3

[Aiden James]

Answer 4

[Aiden James]