Probability plot for von Mises distribution fitted to circular data
circpvm varname [if exp] [in range] [, a(#) grid plot(plot) scatter_options]
circpvm gives a probability (P-P) plot for the fit of a von Mises (a.k.a. circular normal) distribution to a circular variable on a scale between 0 and 360 degrees. circvm is used to fit the distribution, estimating the two parameters vector mean mu and concentration parameter kappa.
For discussion, see Jammalamadaka and SenGupta (2001, pp.218-219); but note that some of their discussion of P-P plots applies to quantile-quantile plots (Q-Q plots), not P-P plots.
a() specifies a in the formula for plotting position. The plotting positions are (i - a) / (n - 2a + 1) for values ranked smallest to largest and assigned unique ranks i = 1, ..., n. The default is a = 0.5, giving (i - 0.5) / n. Other choices include a = 0, giving i / (n + 1), and a = 1/3, giving (i - 1/3) / (n + 1/3).
grid is equivalent to yla(0(.25)1, grid) xla(0(.25)1, grid).
plot(plot) provides a way to add other plots to the generated graph; see help plot_option.
scatter_options are options of scatter.
. circpvm wallasp
Jammalamadaka, S.R. and SenGupta, A. 2001. Topics in circular statistics. Singapore: World Scientific.
Nicholas J. Cox, University of Durham, U.K. email@example.com
On-line: help for circvm, circqvm