dd_plot: dd_plot
In mpadge/distdecay: Calculate Distance Decay Functions

Plot distance decay functions.

1	dd_plot(city, from = TRUE, mi = FALSE, smoother = TRUE)

`city`	City for which distance decay functions are to be plotted.
`from`	Plot covariance or MI values for trips from each station. If `FALSE`, plot equivalent values for trips to each station.
`mi`	If `TRUE`, plot decay functions for mutual information, otherwise plot covariances.
`smoother`	if `TRUE`, overlay a loess-smoothed line. (This will generally take much longer to plot.)