Convert struct to double type in Matlab

Question

Glcm (feature extraction method) give me an output in 'struct' type, while i need the output in 'double' type. I need a 'double' type as the input variable for the next step.

So, I've tried to convert it using several code showed below.

[gl] = glcm (B);
[gl] = struct2cell (gl);
[gl] = cell2mat (gl);
[fetrain] = double (gl);

The code give me an output but it's in 'complex double' type.

Is there a better way to convert 'struct' to 'double' type?

Or to convert 'complex double' to 'double' type?

Any help and suggestion would be very appreciated. Thank you.

Answer 1

First of all, rather than first converting to a cell and then to a matrix, you can convert directly from a struct to a double using struct2array.

fetrain = struct2array(gl);

That aside, there is no difference between a "complex double" and a double. They are both of type double.

class(1i)
% double

You can use real to get the real component of the complex number or abs if you need the magnitude of it.

real(1+1i)
%   1

abs(1+1i)
%   1.4142

In your case this would be:

fetrain_real = real(fetrain);
fetrain_mag = abs(fetrain);

Update

By default struct2array concatenates the data horizontally. If you want your data to be a matrix that is nFields x nData, then you could do something like the following:

fetrain = struct2array(gl);

% Reshape to be nFields x nData
fetrain = permute(reshape(fetrain, [], numel(fieldnames(gl)), numel(gl)), [2 1 3]);