Hi there, I am trying Netlab for Machine Learning in Matlab. Here i want to call the linemin function which uses Brent's minimization method. The documentation says

linemin(F, PT, DIR, FPT, OPTIONS) uses Brent's algorithm to find the minimum of the function F(X) along the line DIR through the point PT. The function value at the starting point is FPT. The point at which F has a local minimum is returned as X. The function value at that point is returned in OPTIONS(8).

I have a function defined in a file f = x.^4 + 10*x.*sin(x.^2); where my x's are from -2:0.1:1. The plot is attached herewith.

I want to know what is the DIR line to start with? In other words what is the direction line in my function through the starting point.