CONTOUR2 Procedure

Draws a contour plot from data stored in an array.

Usage

Input Parameters

A 1D or 2D array containing values of the dependent variable z=z(x, y).

x A 1D or 2D array containing values of the first independent variable. If z is 1D, then x is a required 1D input variable with the same number of elements as z. If z is 2D, then x is an optional 1D or 2D input.

y A 1D or 2D array containing values of the second independent variable. If z is 1D, then y is a required 1D input variable with the same number of elements as z. If z is 2D, then y is an optional 1D or 2D input.

Keywords

C_Fillcolors

Specifies an array of color indices used to fill the contour intervals.

Fill Fills contour intervals with color. This keyword can have the following values:


0	No fill (Default)
1	Filled intervals with contour lines
2	Filled intervals with no contour lines

NOTE: If Fill is specified, labeling is disabled. See Example 2 for information on creating a filled contour plot with labels.

Frequency

A floating-point value

0.0 that determines how frequently labels are printed along the contour. If z is an m-by-n array, the default Frequency value is: MIN(m,n)/3.5. If z is a 1D array of length m, the default Frequency value is: SQRT(m)/3.5.

Label_style An integer specifying the contour label fill style. Possible values are:


0	Do not print labels (Default)
1	Print labels and fill them with the background color. This option takes effect if any other contour label keywords are specified (C_Annotation, C_Charsize, C_Labels, C_Charthick, Frequency).
2	Print labels with a transparent background.
3	Print labels with the fill colors specified by C_Fillcolors.

The CONTOUR2 keywords let you control many aspects of the contour plot's appearance. For a description of each keyword, see Chapter 3, Graphics and Plotting Keywords, in the PV-WAVE Reference.


Background	Gridstyle	[XYZ]Charsize
Channel	Levels	[XYZ]Gridstyle
Charsize	Max_Value	[XYZ]Margin
Charthick	NLevels	[XYZ]Minor
Clip	Noclip	[XYZ]Range
Color	Nodata	[XYZ]Style
C_Annotation	Noerase	[XYZ]Tickformat
C_Charsize	Normal	[XYZ]Ticklen
C_Charthick	Overplot	[XYZ]Tickname
C_Colors	Position	[XYZ]Ticks
C_Labels	Subtitle	[XYZ]Tickv
C_Linestyle	T3d	[XYZ]Title
C_Thick	Thick	[XYZ]Type
Data	Tickformat	ZAxis
Device	Ticklen	ZValue
Font	Title

Discussion

CONTOUR2 provides functionality that CONTOUR does not. CONTOUR accepts only gridded data: the x and y arrays must define a curvilinear coordinate system. CONTOUR2 places no such restriction on x and y, and thus accepts scattered data as well as gridded data.

For scattered data z, x, and y are 1D arrays of the same length.

For gridded data z is a 2D (m by n) array, while x and y can be 2D, 1D, or undefined. If x and y are 2D then they are of dimensions m by n, and z(i,j) corresponds to the point ( x(i,j), y(i,j) ). If x and y are 1D then they are of lengths m and n respectively, and z(i,j) corresponds to the point ( x(i), y(j) ). If x and y are undefined then they default to x = FINDGEN(m) and y = FINDGEN(n).

Example 1

In the example below, randomly scattered data is contoured.

seed0=0 & seed1=2 & seed2=5
z = RANDOMU(seed0, 20)
x = RANDOMU(seed1, 20)
y = RANDOMU(seed2, 20)
CONTOUR2, z, x, y, Nlevels=10, /XStyle, /YStyle

Figure 2-17 Randomly scattered data is contoured.

Example 2

In this example, a filled contour plot with labels is plotted. Labeling is not active for filled plots, so we'll generate the filled plot first, then plot the contour lines with labels over the filled plot using the NoErase keyword. We'll slightly enlarge the size and thickness of the contour labels without affecting the axis text by using the C_Charsize and C_Charthick keywords.

TEK_COLOR

   ; Define a color table.

z = DIST(5)
colorindex=[20, 21, 22]
CONTOUR2, z, /XStyle, /YStyle, NLevels=5, Fill=2, $
        C_Fillcolors=colorindex

  ; Generate a filled plot with no contour lines.

  ; Fill contours with colors defined in the colorindex array.

CONTOUR2, z, /XStyle, /YStyle, NLevels=5, Label_style=3, $
        /NoErase, C_Colors=0, C_Fillcolors=colorindex, $
        C_Charsize=1, C_Charthick=1

  ; Fill contour labels with colors defined in the colorindex array.

Figure 2-18 Contour plot with contour labels and fill color.

CONTOUR2 Procedure

Usage

Input Parameters

Keywords

Discussion

Example 1

Example 2

See Also