How to do this in MATLAB without for loops

Question

S. David 2012-3-12

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Hi,

I have 4 vectors x1, x2, x3, and x4 all of size N-by-1. I need to select two vectors such that their minimum values are the maximum among all. How can I do that in MATLAB without using for loops?

Thanks

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Answer 1

Daniel Shub 2012-3-12

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What about using an Nx4 matrix (or a cell array) instead of x1, x2, ...

In general x1, x2, ... naming is a bad idea:

http://matlab.wikia.com/wiki/FAQ#How_can_I_create_variables_A1.2C_A2.2C....2CA10_in_a_loop.3F

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Answer 2

Andrei Bobrov 2012-3-12

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在 MATLAB Online 中打开

EDIT

n = 4;  
a = eval(['[',sprintf('x%d,',1:n),']']);
[~,idx] = sort(min(a),'descend');
out = a(:,idx(1:2))

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Andrei Bobrov 2012-3-13

Hi Jan! Corrected for general (any) case, when n > 4.

Jan 2012-3-13

There is even no general case of x1, x2, x3, ... as long as Matlab cannot handle x_inf.

I think I should publish a Mex function "Unpoof('x', a, b)", which concatenates the contents of the variables x<a> to x<b> to the variable x and use the ASSIGNIN equivalent to put x into the caller workspace.

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