Could not determine the size of this expression.

Question

mohamed mb 2017-10-11

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/360760-could-not-determine-the-size-of-this-expression

回答： Fred Smith 2017-10-12

采纳的回答： Fred Smith

在 MATLAB Online 中打开

the Embedded MATLAB fail to detemrine the size of my expression(R2017a), i get this problem.

'Could not determine the size of this expression'.

nbclass=max(LS);
for i=0:nbclass-1
       h=plot(Pt(i*nt+1:(i+1)*nt,1),Pt(i*nt+1:(i+1)*nt,2),[style(i+1) color(i+1)]);hold on;
  end;

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Answer 1

Fred Smith 2017-10-12

1
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/360760-could-not-determine-the-size-of-this-expression#answer_285476

在 MATLAB Online 中打开

Mohamed,

What specific expression is MATLAB Coder highlighting? What types do the variables in your code snippet have? What ranges are known? Did you turn dynamic memory allocation off?

At a guess, you have turned dynamic memory allocation off and the problem is this expression:

(i*nt+1 :(i+1)*nt)

Proving that this has a bounded size requires symbolic reasoning beyond MATLAB Coder's abilities. If you rewrite it as follow it should work provided nt is bounded

(i*nt + (1:nt))

However, without reproduction steps this is just a guess.

Note, code generation does not generate code for these plotting routines. They will be evaluated using the MATLAB execution engine when run in MATLAB and not show in standalone code at all.

Thanks,

Fred