MATLAB: Do I receive Undefined function errors for HEAVISIDE function when I try to compile it in a FIT object in MATLAB 7.8 (R2009a)

MATLAB Compiler

I am computing a FIT using the HEAVISIDE function. This works fine inside MATLAB but fails with the following error in my compiled application.
 ??? Error using ==> fittype.fittype>fittype.fittype at 466 
 Expression a.*heaviside(b-x).*(b-x) is not a valid MATLAB expression, 
has non-scalar coefficients, or cannot be evaluated: 
 Error in fittype expression ==> a.*heaviside(b-x).*(b-x) 
 ??? Undefined function or method 'heaviside' for input arguments of type 
 'double'.

Best Answer

The HEAVISIDE function is a function present in the Symbolic Math Toolbox. The Symbolic Math Toolbox functions cannot be compiled using the MATLAB Compiler.
http://www.mathworks.com/products/ineligible_programs/
To workaround this issue, you can write your own heaviside function as shown below:
function Y = heaviside1(X)
%HEAVISIDE    Step function.
Y = zeros(size(X));
Y(X > 0) = 1;
Y(X == 0) = .5;
end
Now, you can use the above custom heaviside function in your MATLAB code as follows:
function my_fit
% Create a fit
x = [1:10]';
y = x*0.25;
z = [-0.5:0.1:0.5];
% Create a FIT
cfit = fit(x,y,'a.*heaviside1(b-x).*(b-x)'); % using custom heaviside1
cfit
d = cfit(z);
plot(x,y,'*k',z,d,'.');
You can then compile this code into a standalone executable using the following command:
mcc -m my_fit.m -a heaviside1.m
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