How to use symbolic variables and functions (Syms) in a Simulink Matlab Function?
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I would like to create a Symbolic function within a Simulink Matlab Function to solve the variables h and t1. Matlab produces error "The function 'syms' is not supported for standalone code generation. See the documentation for coder.extrinsic to learn how you can use this function in simulation." when I try to compile the Simulink Matlab function with the following code.
syms Eq1(h,t1);
Eq1(h,t1) = h*t1;
I tried adding "coder.extrinsic('syms')" at the top, as shown below, and this generated the error "Undefined function or variable 'h'."
coder.extrinsic('syms');
syms Eq1(h,t1);
Eq1(h,t1) = h*t1;
How do I use symbolic variables and functions (Syms) in a Simulink Matlab Function?
采纳的回答
Denis Gurchenkov
2014-9-26
I think the only solution is to use the syms function inside a separate .m file and call that file as extrinsic.
Create a new .m file, e.g. solveSyms.m, put all your code there:
function out = solveSyms(in) % add necessary inputs and outputs
syms x y
f = x^2*y + 5*x*sqrt(y);
out = subs(f, x, in);
end
Now call this new file from the MATLAB Function block:
coder.extrinsic('solveSyms');
out = 0;
out = solveSyms(in);
I'm not very familiar with Symbolic Math toolbox, so you would need to correct the code above to use your equation. Also, read the doc for coder.extrinsic:
6 个评论
SENTHILKUMAR
2014-12-5
but it is showing the error like 'MATLAB expression 'solveSyms' is not numeric.'
Lee
2016-11-30
I solved the problem with @Denis Gurchenkov's answer, Thanks all !
Steven Forest
2017-9-7
I also have this error @ SENTHILKUMAR. How did you solve it?
zhouzhou
2018-7-26
I also have the error @SENTHILKUMAR 'matlab expression 'diff' is not numeric'. How did you solve it?
Emre Deniz
2018-8-1
I have the same problem, 'not numeric'...
In order to use the output of separate .m file in Simulink function, you have to change the type of function output to double. then, it'll work.
function out = solveSyms(in) % add necessary inputs and outputs
syms x y
f = x^2*y + 5*x*sqrt(y);
out = subs(f, x, in);
out = double(out);
end
更多回答（2 个）
Andrew Reibold
2014-9-26
编辑：Andrew Reibold
2014-9-26
Example equation: abs(x+1) + abs(5x-1) = 6
How to solve (Here, I look for real solutions specifically):
syms x real;
solve(abs(x+1)+abs(5*x-2)==6,x);
answer
ans =
7/6
-3/4
Walter Roberson
2016-11-30
Possibly
coder.extrinsic('sym');
coder.extrinsic('symfun');
h = sym('h');
t1 = sym('t1')
EQ1 = symfun(h*t1, h, t1) ;
1 个评论
Walter Roberson
2017-9-7
Note that any of these solutions can only work for "Normal" mode or for "Acceleration" mode, and cannot be used for Rapid Acceleration mode or for code generation to target. No part of the symbolic toolbox can have code generated for it. The use of coder.extrinsic and similar gives a work-around only for Acceleration mode, as there is still a backing MATLAB for that mode.
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