How to get struct value solX.x1 with a symbolic variable x1?

Hello！I have a symbolic expression like

expr=3*x1-2*x3

I solve a equation using vpasolve and get a struct called solX. I can use solX.x1,solX.x2,...to get values.

I want Matlab to find the variables name in the expr and use subs to get the expr value.

variable_Name=symvar(expr)% get 1*2 sym [x1 x3]

I know solX.name(1) is not correct. How to get solX.x1 using variable_Name?

Many thanks!

Answer 1

[Walter Roberson]

solX.(name{1})

However since your goal is symbolic substitution you can probably just do

subs(Expression, solX)

[xv cheng]

Thank you!

solX.(name{1})

It means name should be a cell array ,the element is char,

name={'x1' 'x2' 'x3' ...}

But name=symvar(expr) get 1*2 sym array [x1 x3].So solX.(name{1}) doesn't work.

But at last subs(Expression, solX) It's very simple and useful!Thank you very much!

[Walter Roberson]

name = arrayfun(@char, symvar(YourExpression), 'uniform', 0);

after which you can use solX.(name{1})

But that assumes that all of the symbols in YourExpression appear in solX. If you do not choose to use the shortcut that I posted before of subs(YourExpression, solX) then better would be

subs(YourExpression, fieldnames(solX), struct2cell(solX))