Eigen Library Customized cwise operation - Implementation the "sign()" function in Eigen/C++

In programming language like MATLAB, many coefficient wise operations are provided as function calls: such as sign(M).

For the version of Eigen I currently using, there doesn't seem to have a correspondent build-in implementation cwise operation.

However, a customized cwise operation can be achieve using unaryExpr.

Here is a simple example for achieving similar functionality as the sign() in MATLAB.

float sign(float x)

{

  if (x > 0)

    return 1.0;

  else

    return -1.0;

}

Mat.unaryExpr(std::ptr_fun(sign))