# How can I subtract 2 2D graphs made by vectors of different length?

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Ricardo Fuertes on 6 Jun 2018
Commented: Ricardo Fuertes on 6 Jun 2018
I have 2 sets of data from the same experiment recorded with different methods. The results are 2 graphs describing the same but with some differences. To find those differences I want to subtract the graphs so that I can have a visual representation of where the differences are located.
The problem I have is that the first method has a "X resolution" of 10 data points per second, but the second method's resolution is not constant, sometimes its 7, sometimes its 15. Because of this I can’t just subtract the arrays, since they are not the same length.
Is there a way to do this?

Image Analyst on 6 Jun 2018
Yes, just use interp1() to interpolate them to a common time sequence. If you can't figure it out, attach your two vectors in a .mat file, say what you want the new sampling spacing to be, and someone will do it for you.

#### 1 Comment

Ricardo Fuertes on 6 Jun 2018
Thanks! Its works. I had to remove some data points with the same X value, otherwise I would get 'The grid vectors must contain unique points.' error.

Alfonso on 6 Jun 2018
If you want to quantify the "difference" between 2 datasets of different length, say dataset A with length 100 and dataset B with length 150, you can interpolate the x and y coordinates of dataset A using the "interp1" function to 150 points (length B), then you could for example, calculate the RMSE between the 2 datasets to quantify the differences. (This is one of the ways you could do it)