CODEWITHSUNDEEP
image-processinggraphmatlab
user2178841
user2178841

Reputation: 859

Compare Plots in matlab

I have two plots in matlab where in I have plotted x and y coordinates. If I have these two plots, is it possible to compare if the plots match? Can I obtain numbers to tell how well they match?

Note that the graphs could possibly be right/left/up/down shifted in plot (turning axis off is not problem), scaled/rotated (I would also like to know if it is skewed, but for now, it is not a must).

It will not need to test color elements, color inversion and any other complicated graphic properties than basic ones mentioned above.

If matlab is not enough, I would welcome other tools.

Note that I cannot simply take the absolute difference of x- and y- values. I could obtain x-absolute difference average and y-absolute difference and then average but I need a combined error. I need to compare the graph.

Graphs to be compared.

enter image description here

EDIT

Direct Correlation does not work for me.

For a different set of data: I got .94 correlation. This is very high for given data. noticing that one data is fluctuating less and faster than other.

enter image description here

Upvotes: 1

Views: 3186

Answers (1)

marsei
marsei

Reputation: 7751

You can access the plotted data with this code

x = 10:100;  
y = log10(x);  
plot(x,y);  

h = gcf;  
axesObjs = get(h, 'Children'); %axes handles  
dataObjs = get(axesObjs, 'Children'); %handles to low-level graphics objects in axes  
objTypes = get(dataObjs, 'Type'); %type of low-level graphics object  
xdata = get(dataObjs, 'XData'); %data from low-level grahics objects  
ydata = get(dataObjs, 'YData');

Then you can do a correlation between xdata and ydata for example, or any kind of comparison. The coefficient R will indicate a percent match.

[R,P] = corrcoef(xdata, ydata);

You would also be interested in comparing the axes limits in the graphical current axes. For example

R = ( diff(get(h_ax1,'XLim')) / diff(get(h_ax2,'XLim')) ) + ...
( diff(get(h_ax1,'YLim')) / diff(get(h_ax2,'YLim')) )

where h_ax1 is the handle of the first axe and h_ax2 for the second one. Here, you will have a comparison between values of (XLim + YLim). The possible comparisons with different gca properties are really vast though.

EDIT

To compare two sets of points, you may use other metrics than analytical relationship. I think of distances or convergences such as the Hausdorff distance. A script is available here in matlab central. I used such distance to compare letter shapes. In the wikipedia page, the 'Applications' section is of importance (edge detector for thick shapes, but it may not be pertinent to your particular problem).

Upvotes: 3

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