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Let GraphDraw do all the hard work: Chris Johnson's statistical software

By Chris Williams. Published: 29th Mar 18:59:47 | Permalink | Printable

Despite the large and diverse army of RISC OS freeware applications available on magazine CDs and the internet, there is a very useful statistical utility in particular that I am pleased to see is still being developed to this day. My copy is dated May 1995 and despite its apparent age, I still find it ideal for preparing graphs of empirical data. According to the author, if he had been given a pound every time someone asked him for a Windows version, he could have settled for early retirement. The application in question is GraphDraw and is developed by Chris Johnson.

As previously mentioned, GraphDraw is still being developed and updated. Available now is version 2.59. This release is also a beta release in that the author would like to be informed of any new features or existing problems.

Featurewise, GraphDraw now provides:

  • User definable colours
  • Configurable page format
  • More graph display options can be saved
  • Statistical operations like non-linear least squares fits:

    • log x/linear y
    • linear x/log y
    • log x/log y

  • best straight line
  • best parabola
  • cubic spline curve
  • polynomial of order up to six

With GraphDraw you can input and edit graph x and y values and plot the data using a number of styles and formats, including background grids and axis legends. As stated in Chris' announcement, "The resulting graph may be printed via any standard RISC OS printer driver, saved as a draw file, or exported as a MultiPlot file to allow several graphs to be combined." GraphDraw user manuals, (in Ovation Pro or Impression format), may also be downloaded.

We spoke to Chris about GraphDraw and its history.
"..as far as history goes, believe it or not, the origin of this application can be traced back to the first program I ever wrote on a ZX81, when I produced a simple least squares program, and then added a rudimentary graphing package," explains Chris. "I suddenly realised what might be possible with these new fangled computer things. From there it was soon converted and extended for the ZXspectrum. Once the BBC B arrived, the program was extended again, and was used for several years on the BBC Bs in the physical chemistry labs at Heriot-Watt University. Conversion to the Archimedes followed when I taught myself to write WIMP applications. The program continued to grow, until it became what it is now, forming part of a graphing suite.
"Due to its origins, it was written in BASIC, and once on to the Archimedes series it became compiled BASIC. With the addition of a couple of support modules, which drove the wimp interface, and managed the drawfile production, and which were written in assembler, the combined code amounted to over 15000 lines."

GraphDraw is currently undergoing a complete rewrite. This is an interim
release, in which GraphDraw has been converted to use the Toolbox modules.

"The size of the program code, for GraphDraw in particular, but for many other of my applications as well, has been a distinct disincentive to change language", Chris continues. "However, I have now bit the bullet, and am in the process of converting a number of my applications to C/oslib/toolbox, including GraphDraw. The development of GraphDraw itself has reached the point where it is still in compiled BASIC, but it is now entirely Toolbox based. The next stage will be the actual conversion to C/oslib. Some of my smaller apps have been fully converted, although not yet released to the public, so I am getting there."

Chris also develops MultiPlot, another graphing utility.
"MultiPlot is getting the same treatment, and ultimately I hope my suite of graphing packages will become even more integrated than they are now. MultiPlot already can be used by any application to plot and display graphs, via the standard WIMP messaging protocol. Indeed, if any other programmers out there are interested in linking in to Multiplot, they need only drop me a line for information on the protocols to use. At the moment the file formats are being redesigned to allow the possibility of true OLE with other applications."

GraphDraw 2.59: http://www.graphdraw.riscos.org.uk/
GraphDraw Mailing List: software@chris-johnson.org.uk (send an email to this address stating which software you would like to receive information on)

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