MATLAB: How to execute string variable

evalexecutestrings

can i do this in matlab? %first i want to make a variable named = xxx, and xxx contains MATLAB commands just like this:

xxx = strvcat('x0=5','a=2','c=x0+a')

%but when I use eval, it doesn't work eval(xxx)

Anyone can help me?

Best Answer

xxx = strcat('x0=5;','a=2;','c=x0+a;');
eval(xxx);

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MATLAB: How to summon a double variable that it’s name was stored in a string

Use eval. For example

xxx = 3;     % variable with value
varname = 'xxx';    % name of variable stored as a string
% ... other stuff ...
val_of_xxx = eval(varname);   % gets back value of xxx

But think carefully about whether you really need to do this. It's often the case that there's a better way to write your program, perhaps using structure arrays or cell arrays, that avoids having to store variable names as strings. If there is, it's usually much better to avoid using eval.

MATLAB: Isolate a variable

If your input is x^2 + 2 + x then you cannot isolate x to one side of an equation, as your input is not an equation.

If your input is implicitly x^2 + 2 + x = 0 then your example output of x = x^2 + 2 is incorrect: instead x = -x^2 - 2

You cannot always isolate one variable -- not unless you are willing to make some restrictions on the form of the equation.

If you have a polynomial as input, then

S = x^2+2+x;
c = sym2poly(S);
isolated_x = x * c(end-1) - S;

Best Answer

Related Solutions

MATLAB: How to summon a double variable that it’s name was stored in a string

MATLAB: Isolate a variable

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