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gsn_blank_plot

Draws a blank plot with tickmarks pointing inward.

Prototype

load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl"  ; This library is automatically loaded
                                                          ; from NCL V6.2.0 onward.
                                                          ; No need for user to explicitly load.

	function gsn_blank_plot (
		wks [1] : graphic,  
		res [1] : logical   
	)

	return_val [1] :  graphic

Arguments

wks

A Workstation identifier. The identifier is one returned either from calling gsn_open_wks or calling create to create a Workstation object.

res

A variable containing an optional list of plot resources, attached as attributes. Set to True if you want the attached attributes to be applied, and False if you either don't have any resources to set, or you don't want the resources applied.

Return value

A scalar id of the plot created is returned. This is useful if you want to use setvalues to change some plot options after this function has been called.

Description

This function creates and draws a blank plot with tickmarks pointing inward. By default, the axes will go from 0.0 to 1.0. To change this, you can set trXMinF, trXMaxF, trYMinF, and/or trYMaxF.

If you want the tickmarks to point out, either use gsn_csm_blank_plot, or set gsnTickMarksPointOutward to True.

You can also set any of the Tickmark resources to control their appearance.

The frame is not automatically advanced for this function, so set gsnFrame to True if you need this. To maximize the area that the plot is drawn in, set the special resource gsnMaximize to True.

This function is useful for several purposes:

If you need to create additional tickmarks for a plot (see example 24 on the maps only example page or example 11 on the tickmarks page).
If you need a blank canvas just for drawing primitives (polylines, polymarkers, polygons).
If you need to force an X or Y axis to have irregular spacing, then as of version 6.0.0, you can use this function and set trXCoordPoints and/or trYCoordPoints to an array of unequally-spaced values, and then overlay your existing plot on the blank plot to force your axis to be transformed to one with irregular-spacing (see example 30 on the XY plot page).

In version 6.0.0, gsn_csm_blank_plot was added. This is very similar to gsn_blank_plot, except the tickmarks will automatically point outward, and you can set the special gsnLeftString, gsnCenterString, and gsnLeftString resources to create subtitles at the top.

Examples

For some application examples, see:

"tm_11.ncl" (view example)

Here's a simple example that creates a default "blank" plot.