## generate bivariate normal data
library(MASS)
set.seed(123)
rho <- .85
xy <- mvrnorm(100000, mu = c(0,0), Sigma = matrix(c(1, rho, rho, 1), ncol = 2))
# dichotomize at difficulty values
p1 <- .7
p2 <- .1
xy[,1] <- xy[,1] < qnorm(p1)
xy[,2] <- xy[,2] < qnorm(p2)
print( apply(xy,2,mean), digits = 2)
#[1] 0.700 0.099
tetcor(X = xy, BiasCorrect = TRUE,
stderror = TRUE, Smooth = TRUE, max.iter = 5000)
# $r
# [,1] [,2]
# [1,] 1.0000000 0.8552535
# [2,] 0.8552535 1.0000000
#
# $se
# [,1] [,2]
# [1,] NA 0.01458171
# [2,] 0.01458171 NA
#
# $Warnings
# list()
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