function mse = meanSquaredError(x, y, c)
% Mean squared error between data pairs and a cubic relation.
%
% Arguments: x, vector of the input values
%            y, vector of the corresponding measured output values
%            c, the factor for the cubic relation. 
%
% Returns:   mse, the mean-squared-error.

  mse = mean((y - c*x.^3).^2);
end