# Ngl.vector_scalar_map

Creates and draws vectors, colored by a scalar field, over a map.

## Prototype

vsmap = Ngl.vector_scalar_map(wks, u, v, data, 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*).

*data*

The scalar data field for coloring the vectors. *data* should
be a two-dimensional NumPy or NumPy masked array (dimensioned *ny* x
*nx*).

*res=None*

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

## Return value

*vsmap*

A PlotId representing the map created.

## Description

This function creates and draws vectors, colored by a scalar field,
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 (and the scalar field) where on the map it is being overlaid (in
latitude/longitude degrees). You can do this via the array resources
*vfXArray* (*sfXArray*) and *vfYArray* (*sfYArray*), or the *vfXCStartV* (*sfXCStartV*), *vfXCEndV* (*sfXCEndV*), *vfYCStartV* (*sfYCStartV*), *vfYCEndV* (*sfYCEndV*) resources.

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

## See Also

**Ngl.vector_scalar**,
**Ngl.vector**,
**Ngl.vector_map**,
**Ngl.streamline**,
**Ngl.streamline_map**,

MapPlot resources

VectorPlot resources

ContourPlot resources

VectorField resources

ScalarField resources

LabelBar resources

Title resources

TickMark resources

Transformation resources

View resources

Transform resources

PlotManager resources

Special "ngl" resources

## Examples