Converting/interpolating into different array

I'm trying to figure out how to convert a 25 unit array into a 10 unit array, while interpolating (not sure if that's actually the right word for this) to make sure that the 10 unit array has the correct values. Any help would be greatly appreciated, thanks!

Answer 1

[Arturo Moncada-Torres]

Are you sure is not the other way around? Moving from a 10 element array to a 25 element array you would be interpolation. Moving from a 25 element array to a 10 element array would be decimation.

For decimation:

% Original array
originalArray = 1:25;

% Wished number of samples.
targetSamples = 10;

% Decimation factor.
decimationFactor = length(originalArray)/targetSamples;
decimationFactor = round(decimationFactor); % Decimation factor must be integer.

% Decimation
decimatedArray = decimate(originalArray, decimationFactor);

EDIT

The problem is that DECIMATE allows only integer decimation factors, which not always give you the wished number of samples. Another alternative is the following:

% Original array
originalArray = 1:25;

% Wished number of samples.
targetSamples = 10;

decimatedArray = linspace(originalArray(1), originalArray(end), targetSamples);

Try it and let me know if it works.

[C]

Yes, decimation is the word I was looking for (thank you!). This method posted works, but it only gives me 9 samples instead of 10.

[Arturo Moncada-Torres]

Hello C. Please check the edit. I tried this new alternative and it works =) .

[Walter Roberson]

It might work for consecutive values, but it isn't going to work for (e.g.) originalArray = (1:25).^2;

[C]

This does work but the numbers I'm working with are not consecutive...

Answer 2

[Walter Roberson]

You could use interp1() and play with the interpolation methods that are available.

If the values represent a "signal" then you could fft(), drop components, and fft() the reduced array back.