Table of functions for symbolic expressions

Hello,

I am asking how to declare a table of functions in Matlab for symbolic expressions.

The dimension of my table is n.

%Example : n=3

syms x

T(1) = x^2 ;  T(2) = 2*x-1 ; T(3) = x^3 + 3 ;

Thank you

Answer 1

[Dimitris Kalogiros]

It is not exactly what you asked for, but I believe that it is close enough:

close all
clearvars

syms x n

f(x,n)=piecewise(n==1, 3*x-1, n==2, x^2-1, n==3, log(x))

Look, how it works:

[Abdoulaye Thiam]

I am iterating a process n times, each T(i) is a symbolic expression depending on x. Then T is close to a table. Let me look at your answer.

Thanks

Answer 2

[Walter Roberson]

You cannot create a sym array of functions: the entries stop being functions and become just expressions.

It is possible to create an array of symfun that all have the same arguments, but it is not possible to index into it: effectively what you get is a single symfun that returns a vector or array of results. To get around this you need to use cellfun

See also

https://www.mathworks.com/matlabcentral/answers/378731-how-to-solve-a-symbolic-system-of-first-order-linear-ordinary-differential-equation-using-ode15s-or#comment_614328

which shows additional problems if you try to create the function names dynamically.

For your purpose, I recommend creating an array of symbolic expressions (not functions!) and subs() the value of the argument into the function.

You can put symfun or sym into a table() object, with some care.