NCL Home > Documentation > Graphics > Graphical Interfaces

gsn_vector

Creates and draws a vector plot.

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_vector (
		wks  [1] : graphic,  
		u [*][*] : numeric,  
		v [*][*] : numeric,  
		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.

u
v

The u and v data for the vector plot; must be two-dimensional.

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 vector plot created is returned. The id of the data object is also returned as an attribute called data. This is useful if you want to use setvalues to change some data options after this function has been called.

Description

This function creates and draws a vector plot on the given workstation.

If either u or v have a _FillValue attribute, these values will be used as missing values.

You should use gsn_csm_vector if you want a more customized vector plot and/or if your data has coordinate arrays.

To maximize the area that the plot is drawn in, set the special resource gsnMaximize to True.

Important note: by default, NCL maps the vector direction into the underlying coordinate space. This works well when drawing vectors on a map projection, but for vertical plots where the two coordinate axes have different units with very different numerical spacing between the coordinate values, it leads to distortion. If you are seeing this issue, try setting the resource vcMapDirection to False.

Examples

For some application examples, see:

"meteo_1.ncl" (view example)