How can I use linear interpolation to have two array with the same length?

Hi everyone.

I have a vibration signal with the length of 30,000 for the duration of 10 s. Let's call it "A". I have defined 30 windows with equal lengths of 1,000 samples. For each window length, I have used frequency spectrum to find the highest peak in the frequency components to calculated the rotational speed from the vibration data. So now, I have 30 speed values over time.

Now, I want to use interpolation for the speed data to create a new array including 30,000 speed data points. What I mean is having both vibration and speed with a same length.

I don't know how feasible this idea is. But if it is, I appreciate any help and suggestions.

Thank you

Answer 1

[Matt J]

x=rand(1,30);
xx=interp1(x,linspace(1,30,3e4));

whos x xx

  Name      Size                Bytes  Class     Attributes

  x         1x30                  240  double              
  xx        1x30000            240000  double              

[Ali Safian]

@Matt J Thank you so much, it was a great help. By any chance, do you know how to do achieve the same thing but with quadratic interpolation? I mean extending the number of data point to a desired number.

[Matt J]

I don't know about quadratic, but there are non-linear interpolation choices supported by interp1,

https://www.mathworks.com/help/matlab/ref/interp1.html#btwp6lt-1-method

[Ali Safian]

@Matt J Wondeful, thank you for your help.

[Matt J]

You're welcome, but please Accept-click the answer if your question has been resolved.