simulink error Input ("u") index must be a positive integer in the expression when used for code generation

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David Kenko 2016-5-11

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评论： David Kenko 2016-6-15

I am running MATLAB R2015a and I am attempting to covert a project. When I have my model opened in Simulink and simulate, I get the following error: simulink error Input ("u") index must be a positive integer in the expression when used for code generation

Please, how can I solve the problem?

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Walter Roberson 2016-5-11

Would you happen to be using logical indexing in a MATLAB Function block?

David Kenko 2016-6-13

hello Roberson, no logical indexing, but numerial indexing. I want to simulate my model in Simulink external mode. In my model I have used a FCN-block. Please, do you have an idea how I could solve the problem?. thank you in advance

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Walter Roberson 2016-6-13

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http://www.mathworks.com/help/matlab/ref/strmatch.html

"x = strmatch(str, strarray) looks through the rows of the character array or cell array of strings strarray to find strings that begin with the text contained in str, and returns the matching row indices. If strmatch does not find str in strarray, x is an empty matrix ([])."

Your code does not take into account the possibility that there are no matches.

Also as far as MATLAB can tell at that point, you could be returning multiple values because MATLAB has no way of knowing that there will be only one match.

You will need to use a MATLAB Function block, and in the block you should use strncmp() to build a logical vector of matches. You can then check for the case of no match with ~any() and handle that case, and in the else, you can find(mask, 1, 'first') so that you can be sure you got exactly one result.

Code Generation does not have the flexibility that MATLAB has: it needs to be guided about all these possibilities about no matches, multiple matches, and so on. Even in the case where logically you "know" that you should have exactly one result, you need to fill in the rest for Code Generation because Code Generation wants to be certain that there will be no undefined results in the section it is generating (which might, after all, get reused.)