What does "Lv" mean? I don't know what the L is for.

Below is how I wanted to solve the problem, below that is how it is supposed to be solved. What is that "Lv"? Length?

v= v( v>0 )

x= length( v )

totalsum = sum( v .* sum( A( :, x) ) )

Given a matrix A( m x n ) and a vector v( 1 x n )

Answer 1

[Walter Roberson]

"logical" . A logical vector is built and used to index arrays

[bobsoney bobsoney]

Alright, so in the second sum, shouldn't it be sum(A (:, length( Lv ) ) )? If the logical vector is something such as as [0 1 0 0 0 1 1 0], you can't use it as a dimension.

[Walter Roberson]

research 'logical indexing '

[bobsoney bobsoney]

So basically only the position of the ones counts if you use a logical vector. (?) Therefore making the correct resolution valid.

[Walter Roberson]

yes .