I keep getting this error when using trapz

Hi this error message keeps popping up wheni use trapz and im not sure how to fix it

Error using trapz (line 47)

Dimension argument must be a positive integer scalar

within indexing range.

Error in Hw8_func_crl (line 27)

F= k_p*theta(j) + k_i*trapz(t,theta(j));

Answer 1

[Walter Roberson]

See the explanation at https://www.mathworks.com/matlabcentral/answers/454096-how-to-numerically-integrate-a-non-integer-using-trapz#answer_368799