Kmeans does not accept complex numbers

Why do Matlab says that kmeans does not accept complex data when my data are not complex numbers?

[KSSV]

May be your data has a complex number.

Check:

nnz(~isreal(data))

If the above gives some number, it means your data has complex numbers.

[Walter Roberson]

Put a condition breakpoint on the line that calls kmeans, testing your data. Suppose that your data to be clustered is named Data, then the breakpoint condition could be

any(imag(Data(:)))

and run your code. The problem does not necessarily happen immediately.