array summation with matrices of different size

Question

Saad 2013-1-3

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采纳的回答： Walter Roberson

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Dear All,

I would appreciate some help on this one please.

I am summing matrix elements in different arrays. Say we have 2 arrays:

Price=num2cell(1:10); Coupon=num2cell(1:10);

Price is a cell composed of different matrices. The same for Coupon.

Now the size of the matrices inside "Price" and "Coupon" are not always equal. Of course if I run a code similar to this...

for i=1:10

Price{1,i}+ coupon{1,i};

end

...I get an error which what you would expect because the first matrix of "Price" and "Coupon" are of different size, ....

Now I would like to run an If statement to say: if matrix sizes of Price and Coupon are similar then sum them, if they are not equal then drop that extra elements (at the end) and just sum the first elements. How can I do that please?

example to illustrate: size(Price{1,1})=size(Coupon{1,1})= (1000,1) size(Price{1,2})=(995,1) < size(Coupon{1,2})= (1000,1)

I would like to ignore the extra elements (at the end) of Coupon{1,2} and then sum the remaining elements (i.e. from 1:995) with Price{1,2}? How Can I do that please?

Thanks a lot

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Saad 2013-1-3

thanks a lot for your help

Regards

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Answer 1

Walter Roberson 2013-1-3

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for K = 1:10
   s1 = size(Price{K});
   s2 = size(Coupon{K}};
   common = min(s1,s2);
   rc = common(1);
   cc = common(2);
   Price{K}(1:rc, 1:cc) = Price{K}(1:rc, 1:cc} + Coupon{K}(1:rc, 1:cc);
end

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Saad 2013-1-3

thanks a lot for your help

Regards

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Answer 2

Wayne King 2013-1-3

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编辑：Wayne King 2013-1-3

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When you say "matrices" are they are always really Nx1 column vectors as your example shows? If so you can just do this

    Price = cell(10,1);
    Coupon = cell(10,1);
    Price{1} = randn(995,1);
    Coupon{1}  = randn(1000,1);
    minval = min(length(Price{1}),length(Coupon{1}));
    Price{1} = Price{1}(1:minval);
    Coupon{1} = Coupon{1}(1:minval);
    summ = Price{1}+Coupon{1};

Obviously, you can embed the above in a for loop

     for ii = 1:10
        minval = min(length(Price{ii}),length(Coupon{ii}));
        Price{ii} = Price{ii}(1:minval);
        Coupon{ii} = Coupon{ii}(1:minval);
        summz{ii} = Price{ii}+Coupon{ii};
     end