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1 ## Copyright (C) 1996 John W. Eaton |
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2 ## |
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3 ## This file is part of Octave. |
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4 ## |
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5 ## Octave is free software; you can redistribute it and/or modify it |
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6 ## under the terms of the GNU General Public License as published by |
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7 ## the Free Software Foundation; either version 2, or (at your option) |
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8 ## any later version. |
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9 ## |
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10 ## Octave is distributed in the hope that it will be useful, but |
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11 ## WITHOUT ANY WARRANTY; without even the implied warranty of |
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12 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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13 ## General Public License for more details. |
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14 ## |
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15 ## You should have received a copy of the GNU General Public License |
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16 ## along with Octave; see the file COPYING. If not, write to the Free |
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17 ## Software Foundation, 59 Temple Place - Suite 330, Boston, MA |
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18 ## 02111-1307, USA. |
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19 |
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20 ## usage: logspace (x1, x2, n) |
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21 ## |
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22 ## Return a vector of n logarithmically equally spaced points between |
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23 ## x1 and x2 inclusive. |
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24 ## |
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25 ## If the final argument is omitted, n = 50 is assumed. |
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26 ## |
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27 ## All three arguments must be scalars. |
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28 ## |
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29 ## Note that if if x2 is pi, the points are between 10^x1 and pi, NOT |
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30 ## 10^x1 and 10^pi. |
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31 ## |
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32 ## Yes, this is pretty stupid, because you could achieve the same |
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33 ## result with logspace (x1, log10 (pi)), but Matlab does this, and |
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34 ## claims that is useful for signal processing applications. |
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35 ## |
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36 ## See also: linspace |
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37 |
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38 ## Author: jwe |
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39 |
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40 function retval = logspace (x1, x2, n) |
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41 |
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42 if (nargin == 2) |
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43 npoints = 50; |
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44 elseif (nargin == 3) |
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45 if (length (n) == 1) |
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46 npoints = fix (n); |
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47 else |
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48 error ("logspace: arguments must be scalars"); |
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49 endif |
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50 else |
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51 usage ("logspace (x1, x2 [, n])"); |
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52 endif |
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53 |
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54 if (npoints < 2) |
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55 error ("logspace: npoints must be greater than 2"); |
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56 endif |
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57 |
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58 if (length (x1) == 1 && length (x2) == 1) |
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59 x2_tmp = x2; |
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60 if (x2 == pi) |
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61 x2_tmp = log10 (pi); |
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62 endif |
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63 retval = 10 .^ (linspace (x1, x2_tmp, npoints)); |
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64 else |
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65 error ("logspace: arguments must be scalars"); |
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66 endif |
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67 |
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68 endfunction |
