how to arrange data into array

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Tyler
Tyler on 7 Jan 2021
Edited: Stephen23 on 10 Jan 2021
Hi,
i have imported some matrix data into matlab and upon parsing the data i have it in 3 vectors (columns):
column 1 are the row indices (i.e.):
[1;2;3;4]
column 2 are the column indices (i.e.):
[10;11;13;15]
and column 3 are the values in the matrix associated with those indices (i.e.):
[1e-5;5e-5;10e-5;15e-5]
I'd like to arrange this into a single 2-D array of column 3 data in the row locations of column1, and column locations of column2
I could do this with a loop, but im hoping to find a more elegant / less time intensive solution. I have about a million datapoints.
Thanks alot!
  3 Comments
Tyler
Tyler on 10 Jan 2021
turns out i can use the sparse() command, followed by the full() command to achieve my desired outcome.

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Answers (1)

Stephen23
Stephen23 on 10 Jan 2021
Edited: Stephen23 on 10 Jan 2021
Without an intermediate sparse array:
R = [1;2;3;4];
C = [10;11;13;15];
V = [1e-5;5e-5;10e-5;15e-5];
%
S = max([R,C],[],1);
M = zeros(S); % or NAN
M(sub2ind(S,R,C)) = V % only the first 10 columns are shown below
M = 4×15
0 0 0 0 0 0 0 0 0 0.0100 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.0500 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.1000 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.1500

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