How to define n symbolic variables in Matlab?

Question

I want to define n symbolic variables in Matlab. For example, if the user enters n=3 then compiler defines x1, x2, x3 as symbolic variables (the range of n is unlimited). How can I do this by for loop?

Answer 1

I suppose the same advice holds for symbolic variables as for regular variables:

If you can prevent it, don't create numbered variables. Use a vector instead.

I cannot try it myself, but I believe doc syms will lead you to this:

A = sym('A',dim) %creates a vector or a matrix of symbolic variables.

Answer 2

No need to use a loop.

N = input('How many variables? ');
strArray = [ repmat('x',N,1) dec2base(1:N,10) repmat(' ',N,1)]; % create strings
strArray = strvcat(regexprep(mat2cell(strArray, ...
  ones(1,size(strArray,1)), size(strArray,2)),'x0+','x')).'; % remove heading 0's
str = ['syms ' strArray(:).']; % string to be avaluated
eval(str)

For example, inputing "11", the string

syms x1  x2  x3  x4  x5  x6  x7  x8  x9  x10 x11 

is built and evaluated, which creates the 11 symbolic variables,

Answer 3

Creating a vector as @DennisJaheruddin shows is really the standard way, but if you really need separate variables:

for i = 1:10
    x = sprintf('x%d',i);
    assignin('caller',x,sym(x));
end

Or this will do it in one line:

arrayfun(@(n)assignin('caller',sprintf('x%d',n),sym(sprintf('x%d',n))),1:10)