matrix playing

2011 10 14
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Hi all
i have
w1 =
1.0000 1.0000 1.0000 1.0000 1.0000 1.0000
1.0000 1.0002 1.0000 1.0001 1.0000 1.0001
I want a new matrix with product of all terms in each 2x2 matrix in w1
Eventually, I need a 1x3 matrix.
If I use prod(w1), only the columns get multiplied.
Can anyone help please

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Walter Roberson
Walter Roberson 2011-10-14

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blkproc(w1,[2 2],@prod)

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PChoppala
PChoppala 2011-10-14
w1 =
Columns 1 through 9
1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000
1.0001 1.0003 1.0001 1.0008 1.0002 1.0010 1.0002 1.0009 1.0019
Column 10
1.0000
1.0076
>> blkproc(w1, [2,2],@prod)
ans =
Columns 1 through 9
1.0001 1.0003 1.0001 1.0008 1.0002 1.0010 1.0002 1.0009 1.0019
Column 10
1.0076
this is what I get. All elements in each column are multiplied, I need,
if w1 = [a b c d ; e f g h]
w = [axexbxf cxgxdxh]
Can you help with this?
Walter Roberson
Walter Roberson 2011-10-14
Ah...
blkproc(w1,[2 2],@(x) prod(x(:) )
PChoppala
PChoppala 2011-10-14
Worked, but, just a quick question,
What is 'x'?
Walter Roberson
Walter Roberson 2011-10-14
x is the "formal argument" for the anonymous function. It is nearly exactly like the x in
proc result = multiplyblock(x)
result = prod(x(:));
end

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Image Analyst
Image Analyst 2011-10-14

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Looks like a job for blockproc().
% Generate sample data.
w1 =[...
1.0000 4.0000 1.0000 2.0000 1.0000 6.0000;
1.0000 1.0002 1.0000 1.0001 1.0000 1.0001]
% Declare a function
fun = @(block_struct) prod(block_struct.data(:))
% Do the job:
result = blockproc(w1,[2 2], fun)
Note I changed w1 to make it easier to see that it actually did the job.

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