cplots (version 0.5-0)

scalefactor: Scaling Factor

Description

The function calculates the scaling factor so that after scaling the original density curve (before transformation), the total area after transformation (excluding the reference circle) has the specified value.

Usage

scalefactor(x, radius = 0, total.area = 1, area.prop = TRUE)

Arguments

x

a numeric vector storing the heights of a density curve or a histogram.

radius

the radius of the reference circle.

total.area

a positive number specifying the total area.

area.prop

logical; if TRUE, an area-proportional transformation is applied; if FALSE, a height-proportional transformationis applied.

Value

A numerical value for the scaling factor

Details

Each value in x is a density value before transformation, for points equally-spaced on \([0,2\pi)\). For a smooth density curve, use a reasonably large number of points, equally-spaced on \([0,2\pi)\). The area under the density curve after transformation is then approximated by that of the corresponding sectors. Note if area.prop = TRUE, the scale factor is simply the value of total.area.

References

Xu, D. and Wang, Y. (2020). Area-proportional Visualization for Circular Data. Journal of Computational and Graphical Statistics, 29, 351-357.

See Also

circtrans

Examples

# NOT RUN {
dvm = function(x, mu=0, kappa=1)   # von Mises density
exp(kappa * cos(x - mu)) * (2 * pi * besselI(kappa, 0))^(-1)
x = dvm(seq(0, 2 * pi, len = 100), pi, 10)

scalefactor(x)                            # area-proportional transformation
scalefactor(x, area.prop = FALSE)         # height-proportional transformation
scalefactor(x, total.area = 2)            # total area of 2
scalefactor(x, area.prop = FALSE, total.area = 2)

# }