Code covered by the BSD License

# geom3d

### David Legland (view profile)

19 Jun 2009 (Updated )

Library to handle 3D geometric primitives: create, intersect, display, and make basic computations

### Editor's Notes:

This file was selected as MATLAB Central Pick of the Week

cart2cyl(varargin)
```function varargout = cart2cyl(varargin)
%CART2CYL  Convert cartesian to cylindrical coordinates
%
%   CYL = cart2cyl(POINT)
%   convert the 3D cartesian coordinates of points POINT (given by [X Y Z]
%   where X, Y, Z have the same size) into cylindrical coordinates CYL,
%   given by [THETA R Z].
%   THETA is the arctangent of the ratio Y/X (between 0 and 2*PI)
%   R     can be computed using sqrt(X^2+Y^2)
%   Z     keeps the same value.
%   The size of THETA, and R is the same as the size of X, Y and Z.
%
%   CYL = cart2cyl(X, Y, Z)
%   provides coordinates as 3 different parameters
%
%   Example
%   cart2cyl([-1 0 2])
%   gives : 4.7124    1.0000     2.0000
%
%
%
% ------
% Author: David Legland
% e-mail: david.legland@jouy.inra.fr
% Created: 2006-03-23
% Copyright 2006 INRA - CEPIA Nantes - MIAJ (Jouy-en-Josas).

% process input parameters
if length(varargin)==1
var = varargin{1};
x = var(:,1);
y = var(:,2);
z = var(:,3);
elseif length(varargin)==3
x = varargin{1};
y = varargin{2};
z = varargin{3};
end

% convert coordinates
dim = size(x);
theta = reshape(mod(atan2(y(:), x(:))+2*pi, 2*pi), dim);
r = reshape(sqrt(x(:).*x(:) + y(:).*y(:)), dim);

% process output parameters
if nargout==0 ||nargout==1
if length(dim)>2 || dim(2)>1
varargout{1} = {theta r z};
else
varargout{1} = [theta r z];
end
elseif nargout==3
varargout{1} = theta;
varargout{2} = r;
varargout{3} = z;
end
```