xPx {OasisR} | R Documentation |
A function to compute Bell's isolation index (xPx)
Description
The isolation index, xPx, is an exposure index that measures the probability that two members of a group share the same spatial unit. This index can be calculated using the approximate or the exact method (see Bell, 1954).
Usage
xPx(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 group within spatial units. The number of columns should be greater than 1 (at least 2 groups are required). You should not include a column with total population, 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 numeric vector containing the isolation index values for each group
References
Bell W. (1954) A probability model for the measurement of ecological segregation. Social Forces 32(4), pp. 357-364
See Also
Interaction indices:
xPy
, DPxy
Examples
x <- segdata@data[ ,7:8]
xPx(x)
xPx(x, exact = TRUE)