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Re: Converting z data to matrix
Posted:
Jan 28, 2013 11:11 AM


"Ian " <ikirby23@yahoo.com> wrote in message news:ke0stn$is9$1@newscl01ah.mathworks.com... > Hi guys, > > I wonder if any one could be so kind to help me with what I'm sure is > probably relatively straight forward. If I have x,y, and z data as > follows: > > X= 1 2 3 4 5 > y= 1 2 3 4 5 > z= 8 4 9 7 3 > > Is there any way of making z into the matrix from the above: > > Z= 0 0 0 0 3 > 0 0 0 7 0 > 0 0 9 0 0 > 0 4 0 0 0 8 0 0 0 0
How do you get from x, y, and z to this matrix? If x(k) and y(k) are the indices of the element whose value is z(k) then this should result in a diagonal matrix NOT an offdiagonal. If instead you flipped x then we'd receive the z you requested.
x= [5 4 3 2 1].'; y= [1 2 3 4 5].'; z= [8 4 9 7 3].'; accumarray([x, y], z)
Alternately, if your matrix is going to be sparsely populated (only a small percentage of the elements will be nonzero) then look at the help for SPARSE and use it instead of ACCUMARRAY or use ACCUMARRAY with the ISSPARSE input set to true.
 Steve Lord slord@mathworks.com To contact Technical Support use the Contact Us link on http://www.mathworks.com



