Mercurial > hg > octave-lyh
comparison scripts/statistics/std.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 |
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| 1 function retval = std (a) | |
| 2 | |
| 3 # usage: std (a) | |
| 4 # | |
| 5 # For vector arguments, std returns the standard deviation of the | |
| 6 # values. For matrix arguments, std returns a row vector containing | |
| 7 # the standard deviation for each column. | |
| 8 # | |
| 9 # See also: mean, median | |
| 10 | |
| 11 if (nargin != 1) | |
| 12 error ("usage: std (a)"); | |
| 13 endif | |
| 14 | |
| 15 nr = rows (a); | |
| 16 nc = columns (a); | |
| 17 if (nc == 1 && nr == 1) | |
| 18 retval = 0; | |
| 19 elseif (nc == 1 || nr == 1) | |
| 20 tmp = sum (a); | |
| 21 n = length (a); | |
| 22 retval = sqrt ((n * sumsq (a) - tmp .* tmp) / (n * (n - 1))); | |
| 23 elseif (nr > 1 && nc > 0) | |
| 24 tmp = sum (a); | |
| 25 retval = sqrt ((nr * sumsq (a) - tmp .* tmp) / (nr * (nr - 1))); | |
| 26 else | |
| 27 error ("mean: invalid matrix argument"); | |
| 28 endif | |
| 29 | |
| 30 endfunction |