Measure of the chance variation expected from sample to sample in estimates of the mean direction. The approximated standard error of the mean direction is computed by the mean resultant length and the MLE concentration parameter \(\kappa\).
Arguments
- x
numeric vector. Values in degrees.
- w
(optional) Weights. A vector of positive numbers and of the same length as
x
.- axial
logical. Whether the data are axial, i.e. pi-periodical (
TRUE
, the default) or directional, i.e. \(2 \pi\)-periodical (FALSE
).- na.rm
logical value indicating whether
NA
values inx
should be stripped before the computation proceeds.
Examples
# Example data from Davis (1986), pp. 316
finland_stria <- c(
23, 27, 53, 58, 64, 83, 85, 88, 93, 99, 100, 105, 113,
113, 114, 117, 121, 123, 125, 126, 126, 126, 127, 127, 128, 128, 129, 132,
132, 132, 134, 135, 137, 144, 145, 145, 146, 153, 155, 155, 155, 157, 163,
165, 171, 172, 179, 181, 186, 190, 212
)
circular_sd_error(finland_stria, axial = FALSE)
#> [1] 5.296841
data(san_andreas)
data("nuvel1")
PoR <- subset(nuvel1, nuvel1$plate.rot == "na")
sa.por <- PoR_shmax(san_andreas, PoR, "right")
circular_sd_error(sa.por$azi.PoR, w = 1 / san_andreas$unc)
#> [1] 2.53717