在分配A（I）= B中，B和I中的元素数必须相同

Question

When running this code:

A(B<5) = C + (B-5)*5/10;

I'm getting the following error

In an assignment A(I) = B, the number of elements in B and I must be the same

Where A , B and C are large matrices of same size (6399x6926). I could get it to work using a for loop, but it took more time.

Answer 1

The problem is that size of A(B<5) will typically be smaller then size of A . Size of A(B<5) will be equal to the number of elements of B that obey condition B<5 .

Example:

B=[0 3 8 10]
A=[1 2 3 4]

A(B<5)=[1 2]

This is because only first two elements are less then 5.

Possibly, you wanted to do this:

A(B<5) = C(B<5) + (B(B<5)-5)*5/10;