An alternative to Gnuplot is Gri, written by Dan Kelley and Peter Galbraith. This isn’t quite as daft as it sounds – its a handy way of reminding yourself of options, and can be quicker than looking things up in the manual. Although the point of Gnuplot is scripting, just to confuse you, you can get a GUI front end to Gnuplot – here is a Mac example. It does pretty much everything you need with some minor niggles – for example in SM you can use a column to record a different point type for each data point, whereas in Gnuplot you would have to achieve this by dividing into blocks and using several plot commands. This also means that in interactive mode you can use Gnuplot as a calculator, and some days I prefer this to Python. For example, I have a standard blackbody function, and then in a new script I can just refer to RBB(nu,T). You can define constants and functions, and you can keep your own library of these which you load at startup. In interactive mode it has sensible defaults, so you can just fire up and plot a function or a data file with very little fuss, but it is also very powerful and flexible – for example you can plot arbitrary algebraic combinations of columns, plot parametric functions, and fit datasets. It has a slightly quirky syntax, but is easy to get used to. Outside the astronomy world, what most people know is Gnuplot, started in 1986 by Thomas Williams and Colin Kelley, and continously developed and improved since by an army of volunteers. Pyx begat Pyxplot, as we will see below, but in a manner that never occurs in nature, it replaced the genome while keeping the same phenome. This is an implementation of PGPLOT in Python, which can then be strung together in a Python script, but it doesn’t have the simple syntax of SM or Gnuplot. Two I am aware of are WIP, written for the Owens Valley BIMA array project, and QDP, meaning “Quick and Dandy Plotter”, written by Allyn Tennant at Marshall Space Flight Centre. There have been other front ends for PGPLOT. You have to download the entire rather vast Starlink installation, but you will also get other useful things like Gaia, SPLAT, and ORAC-DR. The Starlink project is no more, but the whole suite is maintained and still available via the Joint Astronomy Centre in Hawaii. (Can’t stop thinking of Pierre Menard.) This was called PONGO as the backend was the PGPLOT library. Back in the Yookay, the Starlink project also re-imagined MONGO. It costs $300 for a single Department-wide license but is “not available for military use”. It is available here, and there is a kind of forum-cum-fansite here. The equally legendary Robert Lupton and Patricia Monger re-implemented Mongo from scratch with added bells and whistles as “Supermongo” or SM. I think the last version was in 1994, and I don’t think you can get it now, but you can still get the documentation here. It was written in F77, and routines can be called from Fortran programmes as well as run interactively. (Yes, that is the same John Tonry who made the vast camera for PanSTARRS ). For astronomers at least, the Mother Of All Plotters is Mongo, written by John Tonry in the 1980s. A nice little script language is what you want, with sensible defaults, so you can just say plot sin(x)/x and leave it that, or you can gradually add sophistication, setting the axes, line weights, etc, saving the script and fiddling more later. On the other hand, pernickety calls to low level routines inside a C programme is just overkill, especially if you already have the data file from somewhere else. Sometimes a GUI based application just doesn’t have enough flexibility, and all that clicking is too laborious. In today’s installment I will look at script based plotters. Part III was about GUI based plotters, wherein I gave healthy plugs to mjograph and the bizarrely named but handy Veusz. Next up, Part II was about mathematical environments, plot libraries, and equation graphers. Just to bring you back up to speed… First there was a general intro. Instead lets have fun ! Yes, lets do the fourth and the final part of the rambling Norse Epic that is my series of posts on plotting software. Too depressed about the pending university cuts to write about that yet.
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