How to set an assumption on a symbolic variable in a symbolic expression?

Hello!

I want to solve some equations using symbolic math toolbox.I only get some strings like '3*x1-2*x2'.x1,x2 should be positive numbers.

I can use str2sym(string) to get a symbolic expression 3*x1-2*x2.

Then, how to set an assumption on x1,x2 in the symbolic expression? The assumption is x1>0,x2>0.

Thank you in advance

Answer 1

[Stephan]

Hi,

you can use the assume function for this purpose.

Note the section for multiple assumptions which requires assumeAlso to work properly.

Best regards

Stephan

[Walter Roberson]

You can symvar to get the variable names and arrayfun assume()