stplanr (version 0.0.2)

dd_loglin: log-linear distance-decay function

Description

'log-linear' distance decay function with two parameters: implementation of the formula used to fit distance to probability of travelling by a given mode by Iacono et al. (2010).

Usage

dd_loglin(x, a = 0.3, b1 = -0.2)

Arguments

x

A positive vector representing distances (often in km)

a

Positive number (usually between 0 and 1) representing the intercept of the distance decay curve with the y axis, when x = 0.

b1

Number representing the 'beta' distance decay parameter. Larger negative values make the initial decay steeper.

References

Iacono, M., Krizek, K. J. and El-Geneidy, A. (2010). Measuring non-motorized accessibility: issues, alternatives, and execution. Journal of Transport Geography, 18(1).

Examples

x <- 0:10 # vector of distances
a = 0.3 # default alpha value
b = 0.2 # default beta value
(res <- dd_loglin(x, a, b))
plot(x, res)

x = seq(0, 50, 0.1)
plot(x, dd_loglin(x))
lines(x, dd_loglin(x, a = 0.1, b1 = 0.15))