Is it possible to vectorize for only one input?

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sykim14
sykim14 2016-6-29
评论： José-Luis 2016-6-29
Suppose there are two variables.
v1 = [1 2 3];
m1 = [1 2 3; 4 5 6];
I hope to create another matrix m2, having the same size with m1, and its (i, j) component is defined by
m2(i, j) = sum(v1 > m1(i, j))
In this case, clearly one solution is use "for" loop twice.
m2 = zeros(2, 3);
for i = 1:2
for j = 1:3
m2(i, j) = sum(v1 > m1(i, j));
end
end
However I want to know whether we can apply vectorization for the above procedure. To do this, I first thought that I may create an anonymous function
test_opr = @(v, x) sum(v > x);
and vectorize for the only latter input(while fixing v). But I couldn't find a proper way to do this. Is there any useful trick or alternative?
Thanks in advance.

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José-Luis
José-Luis 2016-6-29
编辑：José-Luis 2016-6-29
v1 = [1, 2, 3]; m1 = [1, 2, 3; 4, 5, 6];
your_result = arrayfun(@(x) sum(v1 > x), m1)
Though this is just syntactic sugar around looping. Maybe faster, would need to test:
v1 = reshape(v1,1,1,[]);
alt_result = sum(bsxfun(@lt,m1,v1),3)
  2 个评论
sykim14
sykim14 2016-6-29
编辑：sykim14 2016-6-29
Thanks! Your answer helped me a lot. Not just for this specific case, your answer helped me understand arrayfun and bsxfun more deeply.

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