/usr/share/octave/packages/geometry-1.7.0/geom2d/projPointOnLine.m is in octave-geometry 1.7.0-1build1.
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 | ## Copyright (C) 2004-2011 David Legland <david.legland@grignon.inra.fr>
## Copyright (C) 2004-2011 INRA - CEPIA Nantes - MIAJ (Jouy-en-Josas)
## Copyright (C) 2012 Adapted to Octave by Juan Pablo Carbajal <carbajal@ifi.uzh.ch>
## All rights reserved.
##
## Redistribution and use in source and binary forms, with or without
## modification, are permitted provided that the following conditions are met:
##
## 1 Redistributions of source code must retain the above copyright notice,
## this list of conditions and the following disclaimer.
## 2 Redistributions in binary form must reproduce the above copyright
## notice, this list of conditions and the following disclaimer in the
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##
## THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ''AS IS''
## AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
## IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
## ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR
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## DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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## CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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## -*- texinfo -*-
## @deftypefn {Function File} {@var{point} = } projPointOnLine (@var{pt1}, @var{line})
## Project of a point orthogonally onto a line
##
## Computes the (orthogonal) projection of point @var{pt1} onto the line @var{line}.
##
## Function works also for multiple points and lines. In this case, it
## returns multiple points.
## Point @var{pt1} is a [N*2] array, and @var{line} is a [N*4] array (see createLine
## for details). Result @var{point} is a [N*2] array, containing coordinates of
## orthogonal projections of @var{pt1} onto lines @var{line}.
##
## @seealso{lines2d, points2d, isPointOnLine, linePosition}
## @end deftypefn
function point = projPointOnLine(point, line)
# ensure input arguments have same size
if size(line, 1)==1 && size(point, 1)>1
line = repmat(line, [size(point, 1) 1]);
end
if size(point, 1)==1 && size(line, 1)>1
point = repmat(point, [size(line, 1) 1]);
end
# slope of line
dx = line(:, 3);
dy = line(:, 4);
# first find relative position of projection on the line,
tp = ((point(:, 2) - line(:, 2)).*dy + (point(:, 1) - line(:, 1)).*dx) ./ (dx.*dx+dy.*dy);
# convert position on line to cartesian coordinate
point = line(:,1:2) + [tp tp].*[dx dy];
endfunction
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