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1 # Copyright (C) 1993, 1994 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 the |
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7 # Free Software Foundation; either version 2, or (at your option) any |
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8 # later version. |
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9 # |
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10 # Octave is distributed in the hope that it will be useful, but WITHOUT |
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11 # ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
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12 # FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
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13 # 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, 675 Mass Ave, Cambridge, MA 02139, USA. |
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18 |
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19 function [xs, ys] = stairs (x, y) |
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20 |
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21 # usage: [xs, ys] = stairs (x, y) |
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22 # |
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23 # Given two vectors of x-y data, stairs produces a `stairstep' plot. |
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24 # |
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25 # If only one argument is given, it is taken as a vector of y-values |
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26 # and the x coordiates are taken to be the indices of the elements. |
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27 # |
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28 # If two output arguments are specified, the data are generated but |
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29 # not plotted. For example, |
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30 # |
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31 # stairs (x, y); |
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32 # |
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33 # and |
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34 # |
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35 # [xs, ys] = stairs (x, y); |
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36 # plot (xs, ys); |
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37 # |
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38 # are equivalent. |
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39 # |
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40 # See also: plot, semilogx, semilogy, loglog, polar, mesh, contour, |
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41 # bar, gplot, gsplot, replot, xlabel, ylabel, title |
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42 |
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43 |
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44 if (nargin == 1) |
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45 if (is_vector (x)) |
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46 len = 2 * length (x); |
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47 tmp_xs = tmp_ys = zeros (len, 1); |
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48 k = 0; |
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49 for i = 1:2:len |
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50 tmp_xs(i) = k++; |
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51 tmp_ys(i) = x(k); |
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52 tmp_ys(i+1) = x(k); |
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53 tmp_xs(i+1) = k; |
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54 endfor |
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55 else |
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56 error ("stairs: argument must be a vector"); |
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57 endif |
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58 elseif (nargin == 2) |
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59 if (is_vector (x) && is_vector (y)) |
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60 xlen = length (x); |
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61 ylen = length (y); |
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62 if (xlen == ylen) |
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63 len = 2 * xlen; |
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64 tmp_xs = tmp_ys = zeros (len, 1); |
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65 k = 1; |
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66 len_m2 = len - 2; |
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67 for i = 1:2:len_m2 |
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68 tmp_xs(i) = x(k); |
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69 tmp_ys(i) = y(k); |
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70 tmp_ys(i+1) = y(k); |
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71 k++; |
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72 tmp_xs(i+1) = x(k); |
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73 if (x(k) < x(k-1)) |
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74 error ("stairs: x vector values must be in ascending order"); |
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75 endif |
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76 endfor |
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77 tmp_xs(len-1) = x(xlen); |
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78 delta = x(xlen) - x(xlen-1); |
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79 tmp_xs(len) = x(xlen) + delta; |
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80 tmp_ys(len-1) = y(ylen); |
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81 tmp_ys(len) = y(ylen); |
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82 else |
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83 error ("stairs: arguments must be the same length"); |
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84 endif |
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85 else |
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86 error ("stairs: arguments must be vectors"); |
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87 endif |
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88 else |
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89 error ("usage: [xs, ys] = stairs (x, y)"); |
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90 endif |
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91 |
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92 if (nargout == 0) |
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93 plot (tmp_xs, tmp_ys); |
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94 else |
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95 xs = tmp_xs; |
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96 ys = tmp_ys; |
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97 endif |
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98 |
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99 endfunction |
