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% Convert yi back to symfun so output is symfun % Calculate next derivative from previous Yi = % To index into array, yi cannot be symfun N = 0:2 % Increasing orders of differentiation Just use a for loop ( sym/diff is not vectorized in the third argument – see below): syms x y Īlternatively, you could try this form (in this case, for just three indexes, the above will probably be more efficient): syms x y When using symsum, you need to be aware that, like with any Matlab function, the input arguments will be evaluated before being passed in. This occurs because diff(f,x,i) evaluates to zero.

Which returns 0 instead of the correct result indicated above. I think it has something to do with symbolic variables, but I'm new into MATLAB so help will be appreciated. My code should be returning: ans = sin(x) + x*cos(x) - x^2 / 2 * sin(x)

I'm having some problems when using the symsum function in MATLAB's Symbolic Math Toolbox.