Error: Invalid expression. When calling a function or indexing a variable, use parentheses. Otherwise, check for mismatched delimiters.

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Mihir Choughule 2020-5-16

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评论： Stephen23 2025-3-18

Hey guys

I've written some code to compute cost function at various theta, as follows:

h = X * theta;

J = [1/(2*m)] * sum[(h-y).^2];

All variables have been defined. Upon running the code above, I'm getting the following error message:

Error: Invalid expression. When calling a function or indexing a variable, use parentheses. Otherwise, check for mismatched delimiters.

I have no experience with Matlab, so any help would be appreciated!

Thanks

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Rajanya 2025-3-18

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Hi @Mihir Choughule,

'sum' is a function and needs to be called with parentheses (not square brackets [.]) -

sum((h-y).^2)

Thanks.

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Stephen23 2025-3-18

See also: https://www.mathworks.com/help/matlab/learn_matlab/calling-functions.html

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