function gradient = lsqGradient(x, y, parameter)
% The gradient of the least square error
%
% Arguments: x, the input values
%            y, the corresponding measured output values
%            parameter, vector containing slope and intercept 
%                       as the 1st and 2nd element 
%
% Returns: the gradient as a vector with two elements

  h = 1e-6;   % stepsize for derivatives

  partial_m = (lsqError(x, y, [parameter(1)+h, parameter(2)]) - lsqError(x, y, parameter))/ h;
partial_n = (lsqError(x, y, [parameter(1), parameter(2)+h]) - lsqError(x, y, parameter))/ h;

  gradient = [partial_m, partial_n];
end