Outer product of two vectors in Fortran

Unfortunately, no outer product intrinsic function available in Fortran. Outer product return a matrix from two user-provided vector a and b,

where

Fortran Intrinsic Function for Lasso thresholding rule

In Lasso solution, the thresholding rule is

Which can be achieved in Fortran by

sign(dim(abs(a),b),a)