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.
