OasisR (version 2.0.1)

xPy: A function to compute interaction index (xPy)

Description

The interaction index, xPy, is an exposure between groups index which measures the probability that a member of a group shares the same spatial unit with a member of another group. The index can be calculated with the approximate or exact method (see Bell, 1954).

Usage

xPy(x, exact = FALSE)

Arguments

x

- an object of class matrix (or which can be coerced to that class), where each column represents the distribution of a population group, within spatial units. The number of columns should be greater than 1 (at least 2 population groups are required). You should not include a column with total population in each unit, because this will be interpreted as a group.

exact

- a logical variable to specifiy the index version: exact = FALSE (by default) for the approximate version of the index, and exact = TRUE for the exact version

Value

a matrix with interaction index values

References

Bell W. (1954) A probability model for the measurement of ecological segregation. Social Forces 32(4), pp. 357-364

See Also

Isolation indices: xPx, Eta2, DPxx

Distance decay interaction index: DPxy

Examples

# NOT RUN {
x <- segdata@data[ ,1:2]
xPy(x) 
# }