whist {spatstat.univar}

Weighted Histogram

Description

Computes the weighted histogram of a set of observations with a given set of weights.

Usage

whist(x, breaks, weights = NULL, method=c("C", "interpreted"))

Arguments

x

Numeric vector of observed values.

breaks

Vector of breakpoints for the histogram.

weights

Numeric vector of weights for the observed values.

method

Developer use only. A character string specifying whether to use internal C code (method="C", the default) or interpreted R code (method="interpreted").

Details

This low-level function computes (but does not plot) the weighted histogram of a vector of observations x using a given vector of weights.

The arguments x and weights should be numeric vectors of equal length. They may include NA or infinite values.

The argument breaks should be a numeric vector whose entries are strictly increasing. These values define the boundaries between the successive histogram cells. The breaks do not have to span the range of the observations.

There are N-1 histogram cells, where N = length(breaks). An observation x[i] falls in the jth cell if breaks[j] <= x[i] < breaks[j+1] (for j < N-1) or breaks[j] <= x[i] <= breaks[j+1] (for j = N-1). The weighted histogram value h[j] for the jth cell is the sum of weights[i] for all observations x[i] that fall in the cell.

Note that, in contrast to the function hist, the function whist does not require the breakpoints to span the range of the observations x. Values of x that fall outside the range of breaks are handled separately; their total weight is returned as an attribute of the histogram.

Value

A numeric vector of length N-1 containing the histogram values, where N = length(breaks).

The return value also has attributes "low" and "high" giving the total weight of all observations that are less than the lowest breakpoint, or greater than the highest breakpoint, respectively.

Author(s)

Adrian Baddeley [e-mail]

and Rolf Turner [e-mail]

with thanks to Peter Dalgaard.

Examples

  x <- rnorm(100)
  b <- seq(-1,1,length=21)
  w <- runif(100)
  whist(x,b,w)