PyNGL Home > Functions > Graphics routines

Ngl.vector_map

Creates and draws a vector plot over a map.

Prototype

vmap = Ngl.vector_map(wks, u, v, res=None)

Arguments

wks

The identifier returned from calling Ngl.open_wks.

u, v

The U and V components of the vectors. u and v should be two-dimensional NumPy arrays or NumPy masked arrays (dimensioned ny x nx).

res=None

An (optional) instance of the Resources class having PyNGL resources as attributes.

Return value

vmap

A PlotId representing the vector plot created.

Description

This function creates and draws vectors over a map on the given workstation and advances the frame. Plot options can be set via the res variable.

In order to overlay vectors on a map plot, you must tell the vector plot where on the map it is being overlaid (in latitude/longitude degrees). You can do this via the vfXArray/vfYArray resources, or the vfXCStartV/vfXCEndV/vfYCStartV/vfYCEndV resources.

As of version 1.3.0, if u and/or v are masked arrays, then any values equal to the corresponding fill values will not be plotted. If u and/or v are not masked arrays and they contain missing values, then set the resources vfMissingUValueV and/or vfMissingVValueV to these values.

Note that PyNGL internally sets some resources for you, depending on how other resources are set. See the list of default settings for more information.

Examples