# Getting started

Weeds has been distributed with GILDAS since March 2010. Provided that you have installed GILDAS with the Python extension (named PyGILDAS)1 you should have Weeds already installed on your computer. If this is not the case, please refer to the GILDAS documentation for instructions on how to install PyGILDAS.

Let us first start CLASS from a terminal:

    [fontsize=\scriptsize]
    % class
    GILDAS Version: dev (06jun16 15:32) (x86_64-darwin-gfortran-openmp) executable tree

     * Welcome to CLASS

     * Loaded modules
        atm
        sic (J.Pety, S.Bardeau, S.Guilloteau, E.Reynier)
        greg (J.Pety, S.Bardeau, S.Guilloteau, E.Reynier)
        ephem (F.Gueth, J.Pety)
        class (S.Bardeau, J.Pety, P.Hily-Blant, S.Guilloteau)

     * Loaded extensions
        weeds (S.Maret, P.Hily-Blant, J.Pety, S.Bardeau, E.Reynier)

    (...)
    LAS>

Note that the welcome message mentions that the Weeds extension as been loaded. The extension defines a language, named `weeds\`. This language has a number of commands, the list of which can be obtained by typing:

    [fontsize=\scriptsize]
    LAS90> help weeds\

        Weeds is a CLASS extension to analyze spectral surveys or spectral lines
        observations with large bandwidths.  It  provides  several  commands  to
        identify lines on a spectrum and to model it.

        Available commands:
            LID       Identify lines on the current spectra
            LFIND     Find lines from a species within a frequency range
            LLIST     List lines from the line index
            LGET      Get a line from the line index
            LPLOT     Plot a line from the current line index
            MODSOURCE Model the emission of a source at the LTE
            MODSHOW   Show the results of MODSOURCE

        For more information of each command, type 'help <command>'

Each of the commands provided by Weeds has an extensive documentation. Type `help` followed by the command name to read it.