Function for symbolic expression with only some variable among all variables

Question

Marco 2013-1-22

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/59585-function-for-symbolic-expression-with-only-some-variable-among-all-variables

Hi,

I have this symbolic expression:

J =
[ - a2*sin(t1 + t2) - a1*sin(t1), -a2*sin(t1 + t2)]
[   a2*cos(t1 + t2) + a1*cos(t1),  a2*cos(t1 + t2)]
[                              0,                0]
[                              0,                0]
[                              0,                0]
[                              1,                1]

where symvar are:

[ a1, a2, t1, t2]

I saw that I can convert this symbolic expression by matlabFunction command but variables/function-input must be [ a1, a2, t1, t2].

Because I want to put resultant function into a Interpreted MATLAB Function block, how can I assign only t2 as "input" and the others like mask-parameters ? There is a way to convert J to a matlab function with only t2 as input?

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Answer 1

Shashank Prasanna 2013-1-23

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https://ww2.mathworks.cn/matlabcentral/answers/59585-function-for-symbolic-expression-with-only-some-variable-among-all-variables#answer_72073

在 MATLAB Online 中打开

You can use anonymous function to do that. However make sure that the other 3 variables a1 a2 t2 are also defined in the function other wise it will error out.

>> Jfun = matlabFunction(J)
Jfun = 
    @(a1,a2,t1,t2)reshape([-a2.*sin(t1+t2)-a1.*sin(t1),a2.*cos(t1+t2)+a1.*cos(t1),0.0,0.0,0.0,1.0,-a2.*sin(t1+t2),a2.*cos(t1+t2),0.0,0.0,0.0,1.0],[6,2])
>> Jfunt2 = @(t2)Jfun
Jfunt2 = 
      @(t2)Jfun

This was you can call Jfunt2 with only t2 as input arguments, but make sure the other 3 variables are defined someone above.

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Walter Roberson 2013-1-23

在 MATLAB Online 中打开

You would need

Jfunt2 = @(t2)Jfun(a1, a2, t1, t2)

where a1, a2, t1 were defined in scope when the anonymous function was defined.

Walter Roberson 2013-1-23

I am concerned here about whether Simulink MATLAB functions are permitted to use anonymous functions (or function handles). I do not recall that as being one of the permitted datatypes in such functions. I might be getting confused on terminology, though, about which Simulink MATLAB functions are executed in MATLAB as a whole and which ones have to conform to the embedded function requirements.

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