MATLAB: error: A(I) = B中，B和I中的元素个数必须相同

I'm trying to write a code for piecewise linear interpolation using the code my teacher gave the class--it's worth noting that the teacher seemed to have trouble with the equation inside the for loops--and I've run into the error "In an assignment A(I) = B, the number of elements in B and I must be the same." after exiting the loops. I've already looked up the error and know that comes from trying to fit the elements of one array into another of a different size, but I'm not familiar with matrices in MATLAB. Can someone help me understand where my error is coming from?I'm trying to write a code for piecewise linear