Recently I was trying to label some lines in spectra- I asked around to a few python users and got a few methods. All of them were pretty cumbersome though, and required a lot of effort to tailor to my needs.

I searched around on the internet and found this link: http://packages.python.org/lineid_plot/ The source code can be found on github as well: https://github.com/phn/lineid_plot

There are instructions on the page on how to use this handy module that labels lines on a spectrum. The nice part is you just have to make two lists, one with your line locations and the label you want for each respective element in the list. Then you just plot it using the linid_plot.plot_line_ids command that has 4 arguments: xdata list/array, ydata list/array, line wavelengths list, line labels list. You can also still use pylab or matplotlib on the same plot- for instance, I created x and y labels using pylab. The example on the websites above use matplotlib, while I use pylab. You can also still interact with the plot as usual but zooming in, panning, etc. The lines will move with the plot but the labels may go off the screen if you move too far.

I have also included the script (lines.py) I used to generate my spectrum with labeled lines as well as the 3 FITS files of the spectra used in the script. You can see the resultant plot in plot_screenshot.png.

You have to install the lineid_plot module before you can run my script. Matt Davis provided me with this really handy link for installing modules, if you need: http://stsdas.stsci.edu/configuration.html#python

Let the labeling begin.

Also, I should note that I am not the creator of this module, only a happy user. See the github page for author information.

-Jo Taylor