Heading-aware kernel density

Computes an approximate density useful for visualization. For proper circular densities, use hdg_circular() and circular::density.circular().

hdg_density(
  hdg,
  bw = 5,
  kernel = c("gaussian", "epanechnikov", "rectangular", "triangular", "biweight",
    "cosine", "optcosine"),
  weights = NULL,
  n = 512,
  na.rm = FALSE,
  ...
)

# S3 method for class 'hdg_density'
plot(x, main = NULL, xlab = NULL, ylab = NULL, axes = TRUE, ...)

hdg_plot(
  hdg,
  density = hdg_density(hdg, na.rm = TRUE),
  main = NULL,
  xlab = NULL,
  ylab = NULL,
  axes = TRUE,
  ...
)

Arguments

hdg

A heading in degrees, where 0 is north, 90 is east, 180 is south, and 270 is west. Values outside the range [0-360) are coerced to this range using hdg_norm().

bw

The bandwidth of the smoothing kernel. Automatic methods are not available, so you will have to set this value manually to obtain the smoothness you want.

kernel

A kernel algorithm to use

weights

numeric vector of non-negative observation weights, hence of same length as x. The default NULL is equivalent to weights = rep(1/nx, nx) where nx is the length of (the finite entries of) x[]. If na.rm = TRUE and there are NA's in x, they and the corresponding weights are removed before computations. In that case, when the original weights have summed to one, they are re-scaled to keep doing so.

Note that weights are not taken into account for automatic bandwidth rules, i.e., when bw is a string. When the weights are proportional to true counts cn, density(x = rep(x, cn)) may be used instead of weights.

n

the number of equally spaced points at which the density is to be estimated. When n > 512, it is rounded up to a power of 2 during the calculations (as fft is used) and the final result is interpolated by approx. So it almost always makes sense to specify n as a power of two.

na.rm

logical; if TRUE, missing values are removed from x. If FALSE any missing values cause an error.

...

For hdg_density(), dots are unused; for plot.hdg_density(), dots are passed to graphics::lines(); for hdg_plot(), passed to graphics::points()

x

the data from which the estimate is to be computed. For the default method a numeric vector: long vectors are not supported.

main, xlab, ylab, axes

See graphics::plot().

density

A hdg_density() object.

Value

An object identical to stats::density() but with class "hdg_density".

Examples

x <- head(kamloops2016$wind_dir, 1000)
hdg_density(x, na.rm = TRUE)
#> 
#> Call:
#> 	hdg_density(hdg = x, na.rm = TRUE)
#> 
#> Data: x (512 obs.);	Bandwidth 'bw' = 5
#> 
#>        x             y            
#>  Min.   :  0   Min.   :0.000e+00  
#>  1st Qu.: 90   1st Qu.:0.000e+00  
#>  Median :180   Median :0.000e+00  
#>  Mean   :180   Mean   :2.794e-03  
#>  3rd Qu.:270   3rd Qu.:2.000e-09  
#>  Max.   :360   Max.   :4.664e-02  
plot(hdg_density(x, na.rm = TRUE))

hdg_plot(x)