I have an assignment in Matlab and I need to find a function's 8th and 9th derivate. This function is an inline function, as it is an input from the user.
I have been trying to use the function diff, but it tells me: «Function 'diff' is not supported for class 'inline'.»
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f = inline('x^8'); % Our inline function. D8 = diff(sym(f),8) % Find the 8th derivative D8 == prod(1:8) % Check. ans = 1 as expected.
You cannot do symbolic differentiation on inline functions. If you don't have the Symbolic Toolbox, you will have to either consider a specific family of functions and pre-analyze their derivatives. Or, if you want to do numeric differentiation,
t=linspace(0,T,N); f = vectorize(inline(string_from_input)); result = diff(f(t),8)./( t(2)-t(1) )^8;