This is a small package of statistical and graphical functions to accompany the article by Fisher, P.R. & Annesley, S.J. (2006). Slug phototaxis, thermotaxis and spontaneous turning behaviour. Methods in Molecular Biology. 346, 137-170. Ed. L Eichinger & Humana Press. It contains three major functions (and associated auxiliary functions and tables) for the graphical and statistical analysis of slug phototaxis and thermotaxis data – acorn (for accuracy of orientation analysis based on the ordinary von Mises distribution for unidirectional data), bimstat (bimodal statistics based on the von Mises distribution for bidirectional data), and vmtests.on.files (von Mises distribution–based tests on files containing data sets for which κ is hypothesized to be equal in the two-sample and multisample cases). Both acorn and bimstat produce a circular plot of the data along with estimates of the relevant parameters (μ and κ for acorn, α and κ for bimstat), along with confidence limits and tests of their significance (against H₀ that κ = 0 in acorn using the Rayleigh test, against H₀ that α = 0 in bimstat using the LR likelihood ratio test). In each case the data is in the form of one or more files containing a data set consisting of digitized start and endpoints for slug trails in the form “n x1 y1 x2 y2” where n is the slug (or line) number, x1 and y1 are the xy coordinates of the start point, x2 and y2 are the xy coordinates of the endpoint.

The following examples of the use of acorn and bimstat are provided in the package. The commands that produced the output are shown in each case within the plot - they used the data files called "phototaxis_demo" and "bimodal_demo", both of which are provided as part of the DirStats package.

The implementation of the statistical and graphical analysis in DirStats depends on prior installation of the R Environment for Statistical Computing. R can be downloaded from the Comprehensive R Archive Network (CRAN). Precompiled versions are available for Windows, Macintosh and Linux platforms, while the source code is available for porting to other platforms. The directional statistics analysis described here requires the ­circular, CircStats and Bhat packages as well as the R base package. These packages are also available through CRAN. Once R and the required packages have been downloaded and R installed, DirStats should be downloaded and saved as a plain text file called DirStats.R in the R home folder. To install the code, simply run R and type the command source (“DirStats.R”). Save R on exit and the functions in DirStats will then be available permanently. To see the examples above in R use the command DirStats.demo()  after installing DirStats.R.

For more details on how to use DirStats please consult Fisher, P.R. & Annesley, S.J. (2006). Slug phototaxis, thermotaxis and spontaneous turning behaviour. Methods in Molecular Biology. 346, 137-170. Ed. L Eichinger & F. Rivero. In "Dictyostelium discoideum Protocols." Humana Press.