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Naresh
Posts:
7
Registered:
12/7/04


Re: index endpoint to matrix
Posted:
Jan 31, 2013 10:36 AM


"Jos (10584)" wrote in message <kedggo$ild$1@newscl01ah.mathworks.com>... > "Naresh Pai" wrote in message <kec3s0$gl9$1@newscl01ah.mathworks.com>... > > I have a vector with indices, for e.g. > > > > b = [1 4 7] > > > > Using these indices, I am trying to develop a matrix that looks like this > > a =[1 0 0; > > 2 3 4; > > 5 6 7] > > > > In other words, the indices variable (b) indicates endpoints of the matrix a for each row. This looks simple but been trying to figure out how to generalize the code when b could be of different sizes. Any hints would be appreciated. > > > > Thanks, > > Naresh > > I got confused ... what would A look like if B = [4 1 6 2] for instance? > > ~ Jos
Jos, Thanks for your post. B results from a cumsum operation, so it would either ascending (e.g. [1 3 5 9]), or remain constant at some elements ([1 2 2 4]). In the example you provided, the second and fourth element are descending. I have put few other examples to illustrate my requirement. Thanks.
1) b = [2 0 3 4] a = [1 2; 0 0; 3 0 4 0]
2) b = [ 0 3 7 10] a = [0 0 0 0; 1 2 3 0; 4 5 6 7; 8 9 10 0]
3) b = [5 0 0] a = [1 2 3 4 5; 0 0 0 0 0; 0 0 0 0 0]



