Mercurial > octave
comparison scripts/general/tril.m @ 4:b4df021f796c
[project @ 1993-08-08 01:26:08 by jwe]
Initial revision
| author | jwe |
|---|---|
| date | Sun, 08 Aug 1993 01:26:08 +0000 |
| parents | |
| children | 16a24e76d6e0 |
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| 3:9a4c07481e61 | 4:b4df021f796c |
|---|---|
| 1 function retval = tril (x, k) | |
| 2 | |
| 3 # usage: triu (x, k) | |
| 4 # | |
| 5 # Return the lower triangular part of x above the k-th diagonal. If | |
| 6 # the second argument is omitted, k = 0 is assumed. | |
| 7 # | |
| 8 # See also: triu, diag | |
| 9 | |
| 10 if (nargin > 0) | |
| 11 [nr, nc] = size (x); | |
| 12 retval = x; | |
| 13 endif | |
| 14 | |
| 15 if (nargin == 1) | |
| 16 k = 0; | |
| 17 elseif (nargin == 2) | |
| 18 max_nr_nc = max (nr, nc); | |
| 19 if ((k > 0 && k > nr - 1) || (k < 0 && k < 1 - nc)) | |
| 20 error ("tril: requested diagonal out of range") | |
| 21 endif | |
| 22 else | |
| 23 error ("usage: tril (x [, k])"); | |
| 24 endif | |
| 25 | |
| 26 for i = 1:nr | |
| 27 for j = i+1-k:nc | |
| 28 retval (i, j) = 0.0; | |
| 29 endfor | |
| 30 endfor | |
| 31 | |
| 32 endfunction |