For many vectors of data of different length, how do I interpolate to set them all to have the same length?

I'm analyzing a series of data vectors, each of which has a different number of points, but the x-coordinate of the data spans 1 to ~2800. My simulations have 1400 points, so I need to interpolate the data vectors to properly sample the y-coordinate of the data while ending up with all interpolated data vectors at a length of 1400. Are there any helpful tricks? I know "resample()" would do the trick, but I'm not able to purchase the signal processing toolbox, so that's not an option.

Answer 1

[Adam Danz]

Use interp1()

Demo:

xdata = 1:280; 
ydata = 10:150; 

xdataResamp = linspace(xdata(1),xdata(end),numel(ydata)); 
ydataInterp = interp1(xdataResamp,ydata,xdata); 

% Visually inspect results
figure()
plot(xdataResamp,ydata, 'b-o')
hold on
plot(xdata, ydataInterp, 'r-s')

[Blenndrman]

I appreciate you taking the time.

It seems like your code does not change the length of the interpolated vector. If, for example, I begin with a vector that is 1x800 in the x-direction, and end with each being interpolated, except elongated to 1x1400. I think I've confused myself on this!

[Adam Danz]

Hi Brendan,

If I understand your question correctly, your XData are longer than your YData and you'd like to interpolate your YData so it has the same lenght as your XData. Is that correct?

Thats what my answer is doing. ydataInterp is the interpolated YData and has the same length as XData.

plot(Xdata, ydataInterp)

[Blenndrman]

Yes – I figured it out now, your initial answer was correct, and helpful, thanks!

In my actual code I have enough variables that I got confused and misapplied your solution, at first.

[Adam Danz]

Great!