How to import an equation that is user defined in GUI into separate m files?

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Will Sheppard 2018-12-7

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评论： Stephen23 2018-12-9

Hi, I am creating a GUI for a project and I want the user to be able to enter an equation. I then want to run a seperate m file with this equation. I have tried global variables to convert it, but it has not been working for me. Thank you

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Answer 1

Walter Roberson 2018-12-7

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R2017b or later, use str2sym() and then use matlabFunction() with the 'file' option.

R2017b or earlier use sym() and then use matlabFunction with the 'file' option.

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Answer 2

Stephen23 2018-12-7

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编辑：Stephen23 2018-12-7

Use str2func to generate a nice function handle that you can use/pass to your other code.

Note that you will need to prefix the string with '@(x,y,..)', exactly as if you were defining an anonymous function. For example:

>> str = 'sin(x)+sqrt(y)';
>> fun = str2func(['@(x,y)',str]);
>> fun(pi/2,2)
ans =  2.4142

It is best to avoid global variables, evalin, assignin, and other such bad code practices.

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Will Sheppard 2018-12-9

编辑：Will Sheppard 2018-12-9

Right now I have this in the main file and it generates the function handle fine, however I do not get how i use this generated function handle in a seperate .m other than manually entering it.

Stephen23 2018-12-9

"however I do not get how i use this generated function handle in a seperate .m ..."

A function is just a variable in the workspace. You can pass it to a function, just like any other variable.

"...other than manually entering it."

It is not clear what you mean. You do not describe what you tried or what you expect to happen.

Of course you will have to specify where you want to use this function handle: it will not just magically jumpy from where you define it to inside the function where you want to use it. In any case, the simplest, easiest, and most efficient way to pass that function handle to your function is to ensure that your function is written to accept it as an input argument:

fun = str2func(y_in);
yourOtherFun(fun)

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Answer 3

Arvind Sathyanarayanan 2018-12-7

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编辑：Arvind Sathyanarayanan 2018-12-7

Is your m-file a function? If yes, you can pass the variable containing your equation as input argument. You could also send the variable with the equation to the base workspace using the assigin command and evalin the variable into your m-file/function