Left shift is not working
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Hi. I am trying to left shift of a m by n matrix but its not working.
PP = [1 2 3 4 %PP can be any size
1 2 3 4,
1 2 3 4]
I want:
PP = [1 2 3 4
2 3 4 0
3 4 0 0]
I used following code(Here i have to use loop because PP actually a very large size matrrix):
[rows cols]= size(PP);
B = zeros(size(PP));
for i = 1:rows
B = zeros(size(PP));
PP_shift(i, :) = [PP(i,(cols:-1:i)) B(1,(i-1))];
end
PP_shift
But its showing me error. Can anyone please help me? Thanks.
2 Commenti
Knut
il 14 Dic 2011
I dont have Matlab here, but could you not do something like:
[rows cols]= size(PP);
PP_shift = zeros(size(PP));
for i = 1:rows
PP_shift(i,1:end-i+1) = PP(i,i:end);
end
PP_shift
BTW, there is probably some neat 2d/1d way of indexing PP that will give you the desired result with faster execution. Perhaps ind2sub().
Risposte (1)
Walter Roberson
il 14 Dic 2011
If "i" is the number of rows, then why are you using "i" to index the second dimension of B, which is the position for the column number?
Hint: B does not need to be a full-sized array; it could be a vector.
2 Commenti
Walter Roberson
il 14 Dic 2011
Suppose PP is (say) 5 by 3. Then you would create B as 5 by 3 because you create it the same size as PP. Then when you got to row 5 (i=5) you would be trying to index B at (1,i-1) would would be (1,4) which would not exist because B would only be 3 wide.
hint: in your PP_shift line, replace B by the word zeros
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