Incorrect use of '=' operator

Question

Alan Duval 2021-1-4

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链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/708498-incorrect-use-of-operator

评论： Alan Duval 2021-1-4

MATLAB newbie, here.

I'm doing a coding assignment.

This works perfectly fine:

sexq = '(F)emale, (M)ale, (O)ther, (P)refer not to say';

sexa = inputdlg(sexq, 'What is your sex?');

However, when I try to use this:

ageq = 'Participants must be between 18 and 80';

agea = inputdlg(ageq, 'What is your age?');

I consistently get this:

Incorrect use of '=' operator. To assign a

value to a variable, use '='. To compare

values for equality, use '=='.

I've already looked at:

https://uk.mathworks.com/matlabcentral/answers/576694-incorrect-use-of?s_tid=ta_ans_results

I've tried writing it afresh in a new window to see if I'd picked up any text endcoding weirdness having copy/pasted some of the text from a PDF, but it's made no difference. Restarting MATLAB hasn't helped either. Everytime, the first one works, the second one does not.

Thanks in advance.

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Alan Duval 2021-1-4

Thanks for confirming that I havent just missed something, Mathieu and Kalyan.

Alan Duval 2021-1-4

I should say, I'm running 2019a to ensure compatibility with my Mac.

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Answer 1

Fangjun Jiang 2021-1-4

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/708498-incorrect-use-of-operator#answer_590533

编辑：Fangjun Jiang 2021-1-4

Both codes run properly if run alone. You can "clear all" and then try it.

A potential problem is with inputdlg(). "agea" is a cell array. I assume you meant it to be a numerical data.

>> ageq = 'Participants must be between 18 and 80';
agea = inputdlg(ageq, 'What is your age?')
agea =
  1×1 cell array
    {'18'}

You need to convert it to numerical, for example

        >> agea_num=str2double(agea{1})
agea_num =
    18
    

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Fangjun Jiang 2021-1-4

The codes in your original question have no problem by their own. When MATLAB reports an error, it also points to the line of code. You should paste the complete error message.

Alan Duval 2021-1-4