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From: Anthony on 13 May 2010 21:49
Hey,

I am trying to get rid of this loop and possibly use of logical indexing to make this more efficient.

for i=1:length(Returns)
if(Returns(i,:) > 0)
BothPos(i,1) = 1;
else
BothPos(i,1) = 0;
end
end
BothPos = sum(BothPos);

I have a matrix of returns "Returns". And I want to count only if both elements in each row are > 0. Any ideas on how to do this without an if/else.

Thanks
Anthony
From: Walter Roberson on 13 May 2010 22:07
Anthony wrote:

> I am trying to get rid of this loop and possibly use of logical indexing
> to make this more efficient.
> for i=1:length(Returns)
> if(Returns(i,:) > 0)
> BothPos(i,1) = 1;
> else
> BothPos(i,1) = 0;
> end
> end
> BothPos = sum(BothPos);

> I have a matrix of returns "Returns". And I want to count only if both
> elements in each row are > 0. Any ideas on how to do this without an
> if/else.

The whole can be done quite compactly:

sum(all(Returns,2));
From: Anthony on 13 May 2010 23:56
That doesn't seem to work on my matrix. Perhaps I wasn't clear enough in my explanation.

Returns is 252x2. If Returns(i,1) and Returns(i,2) are both > 0 then I want to count. Do this for all the rows and at the end have just the # of times this condition is satisfied.

In loop form again:

for i=1:length(Returns)
if(Returns(i,:) > 0)
BothPos(i,1) = 1;
else
BothPos(i,1) = 0;
end
end
BothPos = sum(BothPos);

Thanks again
Anthony
From: Walter Roberson on 14 May 2010 01:00
Anthony wrote:
> That doesn't seem to work on my matrix. Perhaps I wasn't clear enough in
> my explanation.
>
> Returns is 252x2. If Returns(i,1) and Returns(i,2) are both > 0 then I
> want to count. Do this for all the rows and at the end have just the #
> of times this condition is satisfied.

Yup, my code would do exactly that.

%setup
>> Returns = rand(252,2) > 0.7;

%the code
>> sum(all(Returns,2))
22

%cross-check
>> sum(Returns(:,1) & Returns(:,2))
ans =
22

%after running your code:

>> BothPos
BothPos =
22

From: Bruno Luong on 14 May 2010 01:57
"Anthony " <antfarinaccio(a)gmail.comremove.spam> wrote in message <hsihkj$blf$1(a)fred.mathworks.com>...
> That doesn't seem to work on my matrix. Perhaps I wasn't clear enough in my explanation.
>

You should modify Walter's command to

sum(all(Returns>0,2))

Bruno
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