(swplot-circle)=

# swplot.circle

## Syntax
  
`hPatch = swplot.circle(r0, n, R)`
  
`hPatch = swplot.circle(r0, n, R, nPatch)`
 
`hPatch = swplot.circle(handle, ...)`
 
## Description
  
`hPatch = swplot.circle(r0, n, R)` creates a triangulated patch of a
surface of a circle in 3D, defined by the center position, normal vector
and radius.
   
`hPatch = swplot.circle(handle, ...)` adds the patch object to a given axis
if `handle` is an axis handle or adds the arrow to an existing
[patch](https://www.mathworks.com/help/matlab/ref/patch.html) object, if the given `handle` points to a patch object.
   
  
## Examples
 
Draw 100 random unit circle surfaces with center at $(0,0,0)$ and random
normal vector.
 
```matlab
swplot.figure
N = 100
swplot.circle(zeros(3,N),2*rand(3,N)-1,1)
swplot.zoom(30)% 
```
 
{% include image.html file="generated/swplot_c_1.png" alt="swplot.zoom(30)%" %}
 
## Input Arguments
  
`handle`
: Handle of an axis or triangulated patch object. In case of patch
  object, the constructed faces will be added to the existing object.
  
`r0`
: Center position of the circle in a column vector. Multiple circles can
  be defined using a matrix with dimensions of $[3\times n_{obj}]$ where
  each column defines a circle center.
  
`n`
: Column vector with 3 elements, normal to the circle surface. Multiple
  circles can be defined using a matrix with the same dimensions as `r0`
  parameter.
  
`R`
: Radius of the circle, scalar or row vector with $n_{obj}$ number of
  elements.
  
`nPatch`
: Number of points on the circle circumference, default value is stored in
  `swpref.getpref('npatch')`. The generated patch will contain
  $n_{patch}$ number of faces and vertices.
  
## See Also
  
[swplot.cylinder](#swplot-cylinder)