Routines (alphabetical) > Routines: P > POLAR_SURFACE Procedure

# POLAR_SURFACE Procedure

The POLAR_SURFACE function interpolates a surface from polar coordinates (R, Theta, Z) to rectangular coordinates (X, Y, 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.

## Examples

; Define radius and Theta:
R = FINDGEN(50) / 50.0
THETA = FINDGEN(50) * (2 * !PI / 50.0
; Make a function (tilted circle):
Z = R # SIN(THETA)
; Show it:
SURFACE, POLAR_SURFACE(Z, R, THETA, /GRID)

## Syntax

Result = POLAR_SURFACE( Z, R, Theta [, /GRID] [, SPACING=[xspacing, yspacing]] [, BOUNDS=[x0, y0, x1, y1]] [, /QUINTIC] [, MISSING=value] )

## Return Value

The function returns a two-dimensional array of the same type as Z.

## 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, [x0, y0, x1, y1], 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.

## Version History

Pre-4.0 | Introduced

## See Also

POLAR keyword to PLOT