PyNGL Home > Functions > Graphics routines

Ngl.streamline

Creates and draws a streamline plot.

Prototype

plot = Ngl.streamline(wks, u, v, res=None)

Arguments

wks

The identifier returned from calling Ngl.open_wks.

u, v

The U and V components of the streamlines. 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

plot

A PlotId representing the streamline plot created.

Description

This function creates and draws a streamline plot 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 resource to the one-dimensional NumPy array (of length nx) that represents the X axis, and vfYArray 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, 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