stplanr (version 0.0.2)

dd_logsqrt: log-linear-square-root distance decay

Description

log-linear-square-root distance decay

Usage

dd_logsqrt(x, a, b1, b2)

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. Higher values make the decay steeper.

b2

Number representing the second 'beta' distance decay parameter. Higher values make the decay steeper.

log-linear distance decay (Iacono et al., 2010) with an additional square-root term to make the curve more flexible. The additional term (b2 in the func

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 = seq(0, 50, 0.1)
plot(x, dd_logsqrt(x, a = 0.3, b1 = -0.2, b2 = -0.5), ylim = c(0, 0.5))
lines(x, dd_logsqrt(x, a = 0.3, b1 = -0.2, b2 = 0.5))