Mercurial > hg > octave-nkf
changeset 17490:cff399332a7f
meshgrid.m: Overhaul function.
* scripts/plot/meshgrid.m: Redo docstring and add example and comparison to
ndgrid. Put input validation first. Add %!error blocks for input validation.
author | Rik <rik@octave.org> |
---|---|
date | Wed, 25 Sep 2013 12:37:53 -0700 |
parents | fb5bdabb9169 |
children | 326af26556ea |
files | scripts/plot/meshgrid.m |
diffstat | 1 files changed, 48 insertions(+), 24 deletions(-) [+] |
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line diff
--- a/scripts/plot/meshgrid.m +++ b/scripts/plot/meshgrid.m @@ -21,14 +21,34 @@ ## @deftypefnx {Function File} {[@var{xx}, @var{yy}, @var{zz}] =} meshgrid (@var{x}, @var{y}, @var{z}) ## @deftypefnx {Function File} {[@var{xx}, @var{yy}] =} meshgrid (@var{x}) ## @deftypefnx {Function File} {[@var{xx}, @var{yy}, @var{zz}] =} meshgrid (@var{x}) -## Given vectors of @var{x} and @var{y} and @var{z} coordinates, and -## returning 3 arguments, return three-dimensional arrays corresponding -## to the @var{x}, @var{y}, and @var{z} coordinates of a mesh. When -## returning only 2 arguments, return matrices corresponding to the -## @var{x} and @var{y} coordinates of a mesh. The rows of @var{xx} are -## copies of @var{x}, and the columns of @var{yy} are copies of @var{y}. -## If @var{y} is omitted, then it is assumed to be the same as @var{x}, -## and @var{z} is assumed the same as @var{y}. +## Given vectors of @var{x} and @var{y} coordinates, return matrices @var{xx} +## and @var{yy} corresponding to a full 2-D grid. +## +## The rows of @var{xx} are copies of @var{x}, and the columns of @var{yy} are +## copies of @var{y}. If @var{y} is omitted, then it is assumed to be the same +## as @var{x}. +## +## If the optional @var{z} input is given, or @var{zz} is requested, then the +## output will be a full 3-D grid. +## +## @code{meshgrid} is most frequently used to produce input for a 2-D or 3-D +## function that will be plotted. The following example creates a surface +## plot of the ``sombrero'' function. +## +## @example +## f = @@(x,y) sin (sqrt (x.^2 + y.^2)) ./ sqrt (x.^2 + y.^2); +## range = linspace (-8, 8, 41); +## [@var{X}, @var{Y}] = meshgrid (range, range); +## Z = f (X, Y); +## surf (X, Y, Z); +## @end example +## +## Programming Note: @code{meshgrid} is restricted to 2-D or 3-D grid +## generation. The @code{ndgrid} function will generate 1-D through N-D +## grids. However, the functions are not completely equivalent. If @var{x} +## is a vector of length M and @var{y} is a vector of length N, then @code +## meshgrid will produce an output grid which is NxM. @code{ndgrid} will +## produce an output which is MxN for the same input. ## @seealso{ndgrid, mesh, contour, surf} ## @end deftypefn @@ -44,30 +64,27 @@ y = x; endif - ## Use repmat to ensure that the result values have the same type as - ## the arguments. + ## Use repmat to ensure that result values have the same type as the inputs if (nargout < 3) - if (isvector (x) && isvector (y)) - xx = repmat (x(:).', length (y), 1); - yy = repmat (y(:), 1, length (x)); - else - error ("meshgrid: arguments must be vectors"); + if (! (isvector (x) && isvector (y))) + error ("meshgrid: X and Y must be vectors"); endif + xx = repmat (x(:).', length (y), 1); + yy = repmat (y(:), 1, length (x)); else if (nargin < 3) z = y; endif - if (isvector (x) && isvector (y) && isvector (z)) - lenx = length (x); - leny = length (y); - lenz = length (z); - xx = repmat (repmat (x(:).', leny, 1), [1, 1, lenz]); - yy = repmat (repmat (y(:), 1, lenx), [1, 1, lenz]); - zz = reshape (repmat (z(:).', lenx*leny, 1)(:), leny, lenx, lenz); - else - error ("meshgrid: arguments must be vectors"); + if (! (isvector (x) && isvector (y) && isvector (z))) + error ("meshgrid: X, Y, and Z must be vectors"); endif + lenx = length (x); + leny = length (y); + lenz = length (z); + xx = repmat (repmat (x(:).', leny, 1), [1, 1, lenz]); + yy = repmat (repmat (y(:), 1, lenx), [1, 1, lenz]); + zz = reshape (repmat (z(:).', lenx*leny, 1)(:), leny, lenx, lenz); endif endfunction @@ -104,3 +121,10 @@ %! assert (XX1, XX2); %! assert (YY1, YY2); +%% Test input validation +%!error meshgrid () +%!error meshgrid (1,2,3,4) +%!error <X and Y must be vectors> meshgrid (ones (2,2), 1:3) +%!error <X and Y must be vectors> meshgrid (1:3, ones (2,2)) +%!error <X, Y, and Z must be vectors> [X,Y,Z] = meshgrid (1:3, 1:3, ones (2,2)) +