# Apply a matrix to a function

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Johnny Yoon on 7 Jan 2021
Commented: Johnny Yoon on 25 Jan 2021
Dear Matlab experts,
I would like to apply a matrix into a function as follows.
clear all;
sizee = 1000;
syms 'T' [1 sizee]
T_syms = sym('T', [1 sizee]);
f = sym(zeros(sizee, sizee));
f(:,:) = T1 + T2 + T3 + T4 + ... + T1000; % This is just to make sample equations.
x_vars = (1:1000);
f_ftn (T_syms) = f;
solution = f_ftn(x_vars);
However, I got an error "Symbolic function expected 1000 input arguments but received 1." So, it seems I can't apply a matrix directly to a function. Is there any way that a matrix can be applied to a function? I can use matlabFunction as follows. However, it takes a way too long, like hours. Is there any way which takes a shorter amount of time? Thank you.
f_ftn02 = matlabFunction(f, 'Vars', {T_syms});
solution = f_ftn02(x_vars);
Walter Roberson on 22 Jan 2021
f_ftn02 = matlabFunction(f, 'Vars', {T_syms});
is the way. You could experiment, though, with
f_ftn02 = matlabFunction(f, 'Vars', {T_syms}, 'optimize', false);
As you are not writing to a file, I do not expect it to make any difference, but I saw a recent hint somewhere that some optimization is maybe now being done even when not writing to files, so you could try
Johnny Yoon on 25 Jan 2021

Deepak Meena on 22 Jan 2021
Edited: Deepak Meena on 22 Jan 2021
Hi Johnny,
As far as my understanding goes , it is not possible. Because when you create a symbolic function indexed with a list of syms , the MATLAB will consider it as single entity.
But you can do something like this
clear all;
sizee = 1000;
syms 'T' [1 sizee]
T_syms = sym('T', [1 sizee]);
f = sym(zeros(sizee, sizee));
f(:,:) = T1 + T2 + T3 + T4 + ... + T1000; //or use sum(T_syms)
x_vars = (1:1000);
H(T_syms) = f;
cells = num2cell(x_vars);
H(cells{:});
Johnny Yoon on 25 Jan 2021