how to find the gradient of pixels in angular direction?

i wish to find gradient of pixels which are at an angle of 30 degrees with the central pixel of the block. How can I do this? because the usual gradient operators like sobel,prewitt will allow finding gradient only in the horizontal or vertical direction and not in angular.

Answer 1

[Matt J]

Let H be the horizontal gradient and V be the vertical gradient. Then

 H*cosd(30)+V*sind(30)

will give a directional derivative at 30 degrees.

Answer 2

[Mehri Mehrnia]

If I want to find the norm of edge, should I replace 30 with 90 in the above formula?

Is "H*cosd(30)+V*sind(30)" a vector or point?