## POLAR_SURFACE

The POLAR_SURFACE function interpolates a surface from polar coordinates (R, Theta, Z) to rectangular coordinates (X, Y, Z). The function returns a two-dimensional array of the same type as Z.

This routine is written in the IDL language. Its source code can be found in the file ``` polar_surface.pro``` in the ``` lib``` subdirectory of the IDL distribution.

### Calling Sequence

Result = POLAR_SURFACE( Z, R, Theta )

### Arguments

#### Z

An array containing the surface value at each point. If the data are regularly gridded in R and Theta , Z is a two dimensional array, where Zi,j has a radius of Ri and an azimuth of Thetaj . If the data are irregularly-gridded, Ri and Thetai contain the radius and azimuth of each Zi . Note that the ordering of the elements in the array Z is opposite that used by the POLAR_CONTOUR routine.

#### R

The radius. If the data are regularly gridded in R and Theta , Zi,j has a radius of Ri . If the data are irregularly-gridded, R must have the same number of elements as Z , and contains the radius of each point.

#### Theta

The azimuth, in radians. If the data are regularly gridded in R and Theta , Zi,j has an azimuth of Thetaj . If the data are irregularly-gridded, Theta must have the same number of elements as Z , and contains the azimuth of each point.

### Keywords

#### GRID

Set this keyword to indicate that Z is regularly gridded in R and Theta .

#### SPACING

A two element vector containing the desired grid spacing of the resulting array in x and y . If omitted, the grid will be approximately 51 by 51.

#### BOUNDS

A four element vector, [ x 0 , y 0 , x 1 , y 1 ], containing the limits of the xy grid of the resulting array. If omitted, the extent of input data sets the limits of the grid.

#### QUINTIC

Set this keyword to use quintic interpolation, which is slower but smoother than the default linear interpolation.

#### MISSING

Use this keyword to specify a value to use for areas within the grid but not within the convex hull of the data points. The default is 0.0.

### Example

R = FINDGEN(50) / 50.0 ; The radius.

THETA = FINDGEN(50) * (2 * !PI / 50.0); Theta.

Z = R # SIN(THETA) ; Make a function (tilted circle).

SURFACE, POLAR_SURFACE(Z, R, THETA, /GRID)
; Show it.