r2dtable {stats} | R Documentation |
Generate random 2-way tables with given marginals using Patefield's algorithm.
r2dtable(n, r, c)
n |
a non-negative numeric giving the number of tables to be drawn. |
r |
a non-negative vector of length at least 2 giving the row
totals, to be coerced to |
c |
a non-negative vector of length at least 2 giving the column
totals, to be coerced to |
A list of length n
containing the generated tables as its
components.
Patefield, W. M. (1981). Algorithm AS 159: An efficient method of generating r x c tables with given row and column totals. Applied Statistics, 30, 91–97. doi:10.2307/2346669.
## Fisher's Tea Drinker data.
TeaTasting <-
matrix(c(3, 1, 1, 3),
nrow = 2,
dimnames = list(Guess = c("Milk", "Tea"),
Truth = c("Milk", "Tea")))
## Simulate permutation test for independence based on the maximum
## Pearson residuals (rather than their sum).
rowTotals <- rowSums(TeaTasting)
colTotals <- colSums(TeaTasting)
nOfCases <- sum(rowTotals)
expected <- outer(rowTotals, colTotals) / nOfCases
maxSqResid <- function(x) max((x - expected) ^ 2 / expected)
simMaxSqResid <-
sapply(r2dtable(1000, rowTotals, colTotals), maxSqResid)
sum(simMaxSqResid >= maxSqResid(TeaTasting)) / 1000
## Fisher's exact test gives p = 0.4857 ...