How can I solve an equation and then save the variables in the workspace

I want to solve an equation for a variable in a 'for' loop and then save the variable in the matlab workspace so that I can use the variable for use in further equations.

[James Tursa]

Please provide a simple example or outline of what you need. Typically one might use cell arrays for this (i.e., C{1}, C{2}, etc instead of C1, C2, etc)

[Sreeja]

Thanks James.

A simple example is:

test=[1:0.2:2];

for i=1:length(test)
syms x
vpasolve(test(i)*gamma(x(i))+4==gamma(x(i))*gamma(x(i)),x)
end

I want to solve for x and create a matrix in the work space for each value of test

Answer 1

[John D'Errico]

vpasolve returns a result, however you are just dumping to the command line.

Note the differences in what I did. There are several changes, and they are important.

test=[1:0.2:2];
n = numel(test);
syms x

sym('result',size(test));
for i=1:n
  result(i) = vpasolve(test(i)*gamma(x)+4==gamma(x)*gamma(x),x);
end

result
result =
[ 3.2547273705290590128593428010284, 3.3016632430994950648588106024263, 3.3472332088911943448750737352559, 3.391437577553390151196553596555, 3.4342837920569247618248679670185, 3.4757861221877745059879809666923]

[Sreeja]

Thanks John. But how can I save 'result' as a matrix in the workspace?

[John D'Errico]

It IS a matrix! In fact, here a vector of syms, which is still a matrix just as much as test is. And it is in your workspace.

So what is your real question? Are you asking how to convert it to a vector of doubles? Surely the logical choice for that would be the function double.

I would point out that if that is your goal, then why did you do this symbolically? Why not use fzero? It will surely be faster.

[John D'Errico]

I would also point out that you could have used tools like arrayfun or cellfun to solve problems like this. However a loop is just as good. I think too often we look for the one line, "vectorized" solution in MATLAB, at a great cost in readability.

[Sreeja]

Thanks John for the help..