# Why I can't integrate a matrix in Matlab?

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Jani on 22 Aug 2021
Commented: Jani on 24 Aug 2021
So for a while it worked, but than I ran the program again, and somehow it doesn't work again, though I did not change the code. The error message: "Attempt to execute SCRIPT integral as a function"
The code:
t=3000
a=1.044
b=-3.484*10^(-5)
k=0.0711
n=0.461
for i=1:t
MR(i)=a*exp(-k*(i^(n)))+b*i;
end
fun=@(i) MR;
MRint=integral(fun, 0, 2, 'Arrayvalued', 1)
Wan Ji on 23 Aug 2021

Walter Roberson on 22 Aug 2021
You saved your code into a file named integral.m which is interfering with calling MATLAB's integral() function.
for i=1:t
MR(i)=a*exp(-k*(i^(n)))+b*i;
end
After that, MR will be a vector of constants.
fun=@(i) MR;
That tells MATLAB that fun is an anonmous function that takes a single argument, and no matter what single argument is passed in, it should ignore the argument and return the content of the vector MR. It does not tell MATLAB that MR should be interpreted as a formula in i and integrated based on that formula. When you did the for i=1:t then i was given specific numeric values, 1, 2, 3, and so on, in turn, and that specific numeric value was used to calculate entries for MR.
You could integrate the vector of numeric values with respect to t, but the result is just going to be the numeric values times the difference in times.
Jani on 24 Aug 2021
Okay, Thank you for the explanation!