Plotting Wave Spectra with Python and Diana

This document aims to show how to use Diana to create wave spectra plots from Python scripts and from within the ipython notebook.

Installation

To get access to the Python modules that expose Diana's plotting features, you need to install the python-diana package from the local package repository. Either use the package manager to do this, or enter the following in a terminal:

apt-get install python-diana

Some examples can also be found in the python-diana-examples package.

Importing Modules

You can use Diana's functionality from Python by importing the bdiana and plotcommands modules from the metno package. If you are using an old version of ipython (earlier than version 1.0) then it is also useful to import the embed function from the metno.ipython_extensions module.



In [1]:

    
# Import the modules needed to use Diana.
from metno import bdiana, plotcommands
# Import an extension that lets us embed an image into a worksheet.
from metno.ipython_extensions import embed

Initialisation and Setup

The bdiana module contains the BDiana class. This provides a convenient interface to Diana's functions and also wraps several initialisation steps into one object. To start using Diana, we simply create an instance of this class.



In [2]:

    
b = bdiana.BDiana()
b.setup("/etc/diana/setup/diana.setup-COMMON")

Getting Model Information

The list of models for which data is available can be found by calling the getSpectrumModels method of the BDiana object.



In [3]:

    
models = b.getSpectrumModels()
models

We select one of these models by calling the setSpectrumModel method, then ask for the list of stations for which there is wave spectrum data by calling the getSpectrumStations method.



In [4]:

    
b.setSpectrumModel(models[0])
stations = b.getSpectrumStations()
stations[:5]

We choose to display the data from a station by calling the setSpectrumStation method with the relevant station name. The available times for which data is available are obtained by calling getSpectrumTimes.



In [5]:

    
b.setSpectrumStation(stations[0])
times = b.getSpectrumTimes()

We set the time to use, using the last available time, by calling the setSpectrumTime method before creating an image using the plotSpectrumImage method, embedding the result in this worksheet.



In [6]:

    
b.setSpectrumTime(times[-1])
spectrum_image = b.plotSpectrumImage(500, 500)
embed(spectrum_image)