GLG410 factor of safety function

function fs = factor_of_safety(c, h, theta, prock,m, phi)
%fs = factor_of_safety(c, h, theta, prock,m, phi)
%this function calculates the factor of safety for an infinite slope
%stability problem.  
%See Arrowsmith notes
%note that suggested units are in parenthesis below
%JRA November 22,1999
%
%Variables:
%	external
%	c = cohesion (kg m^-1 s^-2)
%	h = slide mass thickness (m)
%	theta = slope angle in degrees
%	prock = rock density (kg m^-3)
%	m = fraction of saturated thickness (such that m = 0 if the water
%		table is just below the slide surface and m = 1 if the
%		water table is at the ground surface) (dimensionless)
%	phi = angle of internal friction in degrees
%
%	internal
%	g = gravitational acceleration (m s^-2)
%       pwater = water density (kg m^-3)
%	driving = driving stresses
%	resisting = resisting stresses

%set up a couple of constants
%others
	g = 9.81;
	pwater = 1000;

%write the constants back to make sure that it looks right
%fprintf('c = %.3f, h = %.3f, theta = %.3f, prock = %.3f, m = %.3f, phi = %.3f\n', c,h,theta,prock,m,phi);

resisting = (c + h*g*(cos(rads(theta))^2)*(prock-(m*pwater))*tan(rads(phi)));
driving = (prock*h*g*sin(rads(theta))*cos(rads(theta)));
fs=resisting/driving;