PyNGL Home > Functions > Graphics routines

Ngl.vector_scalar

Creates and draws a vector plot with the vectors colored by a scalar field.

Prototype

vs = Ngl.vector_scalar(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

A PlotId representing the vector plot created.

Description

This function creates and draws a vectors, colored by a scalar field, on the given workstation and advances the frame. Plot options can be set via the res variable.

If coordinate values for the X and Y axes are not available, then index values will be used on the axes.

If axes coordinate information is available, then set the vfXArray (sfXArray) resource to the one-dimensional NumPy array (of length nx) that represents the X axis, and vfYArray (sfYArray) to the one-dimensional NumPy array (of length ny) that represents the Y axis. Or, you can optionally send some end point values via the resources 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.

Examples