grad_1d Subroutine

public subroutine grad_1d(x, u, dudx, undef)

Calculate gradient of "u" in one dimension based on the 2nd order central differential approximation:
$\frac{\partial u}{\partial x}\approx \frac{u_{i+1}-u_{i-1}}{2dx}$

Arguments

Type	Intent	Optional	Attributes		Name
double precision,	intent(in)			::	x(:)	Axis point
double precision,	intent(in)			::	u(size(x))	Target variable
double precision,	intent(out)			::	dudx(size(x))	du/dx
double precision,	intent(in)			::	undef	undefined dudxue