Question

Basically, I need to understand what this piece of code does (“blocks” is a vector):

len = length(blocks);
currsum = sum(abs(blocks(i:1:len)));

I know what the sum and abs does, it’s just the last part, I know it’s something to do with the loop, however, does it take a specific part of the vector and get the sum, or, does it sum the entire vector up?

Answer 1

Let’s break this into parts:

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 i:len

Create a vector [i, i+1, i+2,.... len]. Recall that in Matlab the operator vec(indexes) selects the elements of the vector that are found in indexes.

 blocks(i:len)

Take the last k elements from the i’th up to the last.

 abs(  blocks(i:len) )

Absolute value of the last k elements.

 sum(abs(blocks(i:1:len)));

Sum of the absolute value of the last k elements.