computational time nested if commands

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Stelina 2014-9-9

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https://ww2.mathworks.cn/matlabcentral/answers/154128-computational-time-nested-if-commands

编辑： Andrei Bobrov 2014-9-10

采纳的回答： Andrei Bobrov

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Hi there,

I am attaching an mfile with nested ifs - it is really simple and I include the commenting, so it is easily read.

However, it takes for ever to execute. The weird thing is that if I exclude only one condition (one nested if - the >1.11 Z see code) , it executes really fast. I really cannot spot weather there is a mistake in the code - it doens't return anth as an error, just simply never stops, so I was just hoping for you MATLAB guru's.

Thanx a lot in advance! Stella

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Answer 1

Andrei Bobrov 2014-9-9

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https://ww2.mathworks.cn/matlabcentral/answers/154128-computational-time-nested-if-commands#answer_151161

编辑：Andrei Bobrov 2014-9-10

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us1 = abs(Us(:,1:48));
x = us1(:,[1:30,36:48]);
z = us1(:,[31,32,34,35]);
p = us1(:,33);
l1 = all([bsxfun(@gt,p,2*x),2), bsxfun(@gt,p,1.11*z)],2);
Usvalid = Us(l1,:);
Usnonvalid = Us(~l1,:);

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Stelina 2014-9-9

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Andrei thanx for the answer. If I understand correctly, the code is equivalent with (i was getting error):

us1 = abs(Us(:,1:48));   
x = us1(:,[1:30,36:48]);
z = us1(:,[31,32,35,36]);
peak = us1(:,33);
criterion1=bsxfun(@gt,peak,2*x)    
criterion2=bsxfun(@gt,peak,1.11*z)  
l1 = all([criterion1, criterion2],2);
 Usvalid = Us(l1,:);

I get correct results. However, since criterion1 and criterion2 are my new arrays as returned by bsxfun, how does the all command above work?

And, still, do you perhaps have any idea what was going wrong with the first code with the nested ifs?

Thanx, Stella

Andrei Bobrov 2014-9-10

编辑：Andrei Bobrov 2014-9-10

在 MATLAB Online 中打开

variant with loop for..end and condition if..else..end:

us1 = abs(Us(:,1:48));   
x = us1(:,[1:30,36:48]);
z = us1(:,[31,32,35,36]);
peak = us1(:,33);
k = 0;
m = 0;
for ii = 1:size(Us,1)
    if all(peak(ii) > 2*x(ii,:)) && all(peak(ii) > 1.11*z(ii,:))
        k = k + 1;
        Usvalid(k,:) = Us(ii,:);
    else
        m = m + 1;
        Usnonvalid(m,:) = Us(ii,:);
    end
end