Clear Filters
Clear Filters

How to count in arrays?

2 views (last 30 days)
Evelyn
Evelyn on 17 Nov 2014
Commented: John D'Errico on 17 Nov 2014
Let's say I have two arrays
apple = [1 2 3 4 5 6 7 8];
pear = [2 3 1 2 7 6 1 8];
I want to compare these arrays and count how many items in pear are bigger than the item at the same place in apple. How would I do this?
  1 Comment
the cyclist
the cyclist on 17 Nov 2014
Edited: the cyclist on 17 Nov 2014
Sounds like homework. Here are a few hints:
  • There is "greater than" operator in MATLAB, which will operate on vectors
  • There is also an operator that will sum over a vector
  • There is a docsearch command that will search the documentation

Sign in to comment.

Accepted Answer

Manoj
Manoj on 17 Nov 2014
x=sum(pear>apple);
  1 Comment
John D'Errico
John D'Errico on 17 Nov 2014
While this correct, I recall that it will be slightly faster to use nnz instead of sum.
x = nnz(pear > apple);
The difference will be small unless the arrays are significantly large.
pear = round(rand(1,1e7)*10);
apple = round(rand(1,1e7)*10);
timeit(@() sum(pear > apple))
ans =
0.03888
timeit(@() nnz(pear > apple))
ans =
0.023221

Sign in to comment.

More Answers (0)

Categories

Find more on Creating and Concatenating Matrices in Help Center and File Exchange

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!