How do you take the absolute value of only the complex number?

I have a matrix of 128x256 filled with real and complex number; ex. -0.0115+0.0059i.

How do I take the absolute value of only the complex number so that it becomes -0.0115 + abs(0.0059i)?

I would like to apply this to all the cells in the matrix.

[James Tursa]

Did you really mean abs(0.0059i) with the i inside the abs( ) function as written? Or did you just mean abs(imag coeff)*i?

Answer 1

[Jon]

x = -0.0115+0.0059i
xnew = real(x) + abs(imag(x))*i

[Jon]

This will work for a m by n matrix too.

X = randn(128,256) + randn(128,256)*i;
Xnew = real(X) + abs(imag(X))*i

Answer 2

[Walter Roberson]

NewArray = complex(real(YourArray), abs(imag(YourArray)));

or

NewArray = real(YourArray) + 1i .* abs(imag(YourArray));

Using complex() should be slightly more efficient.

There is a very slight difference in the results between the two: In the case where the imaginary components of the array are all 0, then the + 1i .* form would be adding 1i .* 0 which would all vanish and the end result in NewArray would be marked as entirely real-valued. But if you use complex() then even if the final result has all-zero in the imaginary component, the result will be marked as complex, and will have storage allocated for the complex part.

For most purposes, whether the all-zero imaginary part is stored or not makes no difference. But it can make a difference when you are calling library routines that are expecting a complex array, especially if you are expecting them to update the array "in-place"