OPLOT Procedure

Plots vector data over a previously drawn plot.

Usage

Input Parameters

A vector. If only one parameter is supplied, x is plotted on the y-axis as a function of point number.

y (optional) A vector. If two parameters are supplied, y is plotted as a function of x.

Keywords

OPLOT keywords let you control many aspects of the plot's appearance. These keywords are listed below. For a description of each keyword, see

Chapter 3, Graphics and Plotting Keywords


Background	Normal	[XYZ]Gridstyle
Channel	Nsum	[XYZ]Margin
Charsize	Polar	[XYZ]Minor
Charthick	Position	[XYZ]Range
Clip	Psym	[XYZ]Style
Color	Save	[XYZ]Tickformat
Data	Solid_Psym	[XYZ]Ticklen
Device	Subtitle	[XYZ]Tickname
Font	T3d	[XYZ]Ticks
Gridstyle	Thick	[XYZ]Tickv
Linestyle	Tickformat	[XYZ]Title
Noclip	Ticklen	[XYZ]Type
Nodata	Title	YNozero
Noerase	[XYZ]Charsize	ZValue

Discussion

OPLOT differs from PLOT only in that it does not generate a new axis. Instead, it uses the scaling established by the most recent call to PLOT and simply overlays a plot of the data on the existing axis. Each call to PLOT establishes the plot window (the region of the display enclosed by the axes), the axis types (linear or log), and the scaling. This information is saved in the system variables !P, !X, and !Y, and used by subsequent calls to OPLOT.

Example

In this example, 10 random points are plotted as square markers using the PLOT procedure. Procedure OPLOT is then used to plot a cubic spline interpolant to the random points. The square markers at the random points remain in the plotting window when the interpolant is plotted because OPLOT draws over what is already in the plotting window. This example uses the PV-WAVE:IMSL Mathematics Toolkit and PV-WAVE:IMSL Statistics Toolkit functions CSINTERP, RANDOMOPT, RANDOM, and SPVALUE.

RANDOMOPT, Set = 45321

; Create a vector of 10 random values.

x = RANDOM (10)
PLOT, x, Psym = 6

; Plot the random points as a function of vector index. Use square
; marker symbols to represent the data points.

pp = CSINTERP(FINDGEN(10), x)
ppval = SPVALUE(FINDGEN(100)/10, pp)

; Compute the cubic spline interpolant.

OPLOT, FINDGEN(100)/10, ppval

; Plot the interpolant over the marker symbols (see Figure 2-57).

Figure 2-57 Overplotting a plot.

Figure 2-58 Overplotting a plot.

See Also

For more information, see Chapter 4, Displaying 2D Data, in the PV-WAVE User's Guide.

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