# scalefactor: Scaling Factor In cplots: Plots for Circular Data

 scalefactor R Documentation

## 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.

### Details

Each value in x is a density value before transformation, for points equally-spaced on [0,2π). For a smooth density curve, use a reasonably large number of points, equally-spaced on [0,2π). 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`.

### Value

A numerical value for the scaling factor

### Author(s)

Danli Xu <dxu452@aucklanduni.ac.nz>, Yong Wang <yongwang@auckland.ac.nz>

### References

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

`circtrans`

### Examples

```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)

```

cplots documentation built on March 24, 2022, 9:05 a.m.