[Solved] Upsampling multidimensional array with interpn

Hi all,

I'm trying to upsample a multidimensional array. Here is the code that I used for a monodimensional array:

sf1 = 100; %original sampling frequency
time = (0:(1/sf1):10-(1/sf1))'; %time array
x = randn(length(time), 1);

sf2 = 200; %final sampling frequency
upTime = (0:(1/sf2):10-(1/sf2))';
y = interp1(time, x, upTime);

Now I would like to upsample a 5D array, such as:

z = [randn(length(time), 1) randn(length(time), 1) randn(length(time), 1) randn(length(time), 1) randn(length(time), 1)];

How Can I use the interpn function properly?

Thank You all!

Answer 1

[John D'Errico]

That is NOT a 5 dimensional array.

While you may THINK of it as a set of points that live in 5 dimensions, it is NOT a 5-d array. You CANNOT use interpn to interpolate that data. NOT. Period. NOT.

THIS is a 5-dimensional array:

A = rand(2,3,4,5,6);
size(A)
ans =
     2     3     4     5     6

You can then use tools like griddatan or scatteredInterpolant to interpolate such data.

If you want to view the data as 5 independent streams of ONE dimensional data, then you can still use interp1 to interpolate. For example:

A = rand(100,5);
t = (1:100)';
interp1(t,A,7.25)
ans =
      0.35284     0.051081      0.32818      0.34913      0.75639

Only you know what the array represents. By themselves, numbers are just numbers. Only you know what they represent.

[Johnny Scalera]

You are right! This is the correct solution

y1 = interp1(time, z, upTime);

Thank you!

[John D'Errico]

Excellent. It almost had to be one of those two cases.