problem writing a seemingly easy summation

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alexaa1989
alexaa1989 2014-8-15
评论： Adam 2014-8-15
hi everyone I have this matrix P and for each column j I need to have a summation from second row to end, or i=2:end
for example
P=[1 3 5 7;3 5 7 9;2 4 6 8];
now the matrix I am looking for is [5 9 13 17]
but no matter how I try to write it the answer is second row only
can someone help?
thank u in advance

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Adam
Adam 2014-8-15
sum( P(2:end,:) )
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Adam
Adam 2014-8-15
Can you paste in the whole Matlab commands with results output to command line? In the answer below you said it gave 34 so it sounds as though something odd is happening with your code or your Matlab.
I get exactly the same as Guillaume posted when I run this command.
sum (and most functions of that type) on a 2d matrix will, by default sum each column and give you a result which is 1-by-numColumns.

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Guillaume
Guillaume 2014-8-15
sum(P(2:end, :))
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alexaa1989
alexaa1989 2014-8-15
is it possible that I have been using false data???!!!!

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