Xpf = dirdiff(X,f,p)

generates directional derivative of symbolic scalar function f at the point p in the direction of symbolic vector X(p). p must be a cell array {p1,p2,..pn} of doubles or symbolic variables.

examples
syms x1 x2 x3 y1 y2 y3
X = [ 2*x3 - x1^2 ; x1^3 - x3^2 ; x2^4 ] ;
f = x1^2 + x2^2 + x3^2 ;
dirdiff(X,f,{2,0,3}) returns Xpf = 3.5777
dirdiff(X,f,{y1,0,0}) returns Xpf = -2*y1^3/(y1^4+y1^6)^(1/2)