1. Invoking the Jython Library and Editor
• Click on the main menu item Edit→Formulas→Jython Library to bring up the Jython Libraries Editor

The Jython Library window has two or more panes selected by the tabs at the top. Only the "User's Library" is editable; the others came from the site path and system defaults.

How to Edit in the Jython Library and for more info see How to write a Jython Method and Jython Methods and the IDV
2. Defining your own Jython Method
• In the Jython libraries Editor, click on the tab User's Library
• Create a new Jython method called windSpeed(u,v). Jython methods have a first line beginning with "def" and ending with the colon ":". The code block composing the method must be indented at least one space. Indentation must be the same for all line in a code block, except continued comment lines which are set off with triple quotes. Your code block will be something like:

   
  def  windSpeed(u,v):
       """  compute wind speed from u and v
            wind components """
       usqd= u*u
       vsqd= v*v
       ws = sqrt(usqd + vsqd)
       return ws
  

• Click on Save to check for correct Jython syntax and save the method; you will get an error message if the syntax is not correct. If it is complete, your method is saved.
• Use the File→Close menu to exit the editor.
3. Use the Method in a Formula
• Leave up your previous display made with formulas, and the same data source.
• From the main menu, click on Edit→Formulas→Create Formula. The Formula Editor window appears.
• Enter the Name jythonWS.
• Enter the method for the formula definition in the Formula entry field, simply windSpeed(u,v).
• Open the Advanced panel by clicking on the down arrow.
• Enter the Description "jython wind speed".
• For Group select Workshop from the drop down list.
• In the Displays section, click on Use selected and then the All off radio button. Then select Contour Plan View and Contour Vertical Cross Section in the list.
• Click on Add Formula.
• An item jython wind speed should appear in the Field Selector window's Fields panel, under the Workshop category.
• Use the formula to make a contour display of wind speed using the same u and v wind components from the previous exercise.
• Check to see if the results appear reasonable.

Unidata IDV Workshop for version 5.7 > Advanced Topics > Diagnostic Functions: Formulas and Jython