local_density_2d: 2d local density estimate.
In hadley/densityvis: Common interface to a range of density calculations.

2d local density estimate.

1 2	local_density_2d(x, y, weight, scale=TRUE, nn=0.7, h=0, kernel="tcub", degree=2, bounded=FALSE, na.rm=FALSE)

`x`	a numeric vector of x positions
`y`	a numeric vector of y positions
`weight`	`NULL` or a numeric vector providing weights for each observation
`h`	constant bandwidth. Use if you want a constant bandwith, rather than a bandwidth that varies. If both `nn` and `h` are set, each is calculated for each location and the largest is used. If `scale = TRUE` the unit of this value is standard deviations, otherwise, it's in the units of the data.
`nn`	A vector of length two, giving the span, or nearest neighbour fraction, the proportion of the total used to compute the density.
`scale`	should x and y positions be scaled independently? Use `FALSE` when variables are measured on the same original scale.
`kernel`	Weight function, default is tricubic. Other choices are `"rect"`, '"trwt"', '"tria"', '"epan"', '"bisq"' and '"gauss"'. Choices may be restricted when derivatives are required; e.g. for confidence bands and some bandwidth selectors.
`degree`	degree of polynomial used for smoothing
`bounded`	if `TRUE` bounds density to range of data, otherwise it takes non-zero values over the entire real plane.
`na.rm`	If `TRUE` missing values will be silently removed, otherwise they will be removed with a warning.

data(baseball, package = "plyr")
dens <- local_density_2d(baseball$g, baseball$ab)
plot(dens)
baseball$dens <- dens(baseball$g, baseball$ab)

plot(local_density_2d(baseball$g, baseball$ab, nn = 0.4))
plot(local_density_2d(baseball$g, baseball$ab, nn = 0.1))
plot(local_density_2d(baseball$g, baseball$ab, bounded = TRUE))