fixing_function.r

require(pscl)

# the vuong test returns NULL. Lines below will modify the function to return the output table:
# Turn the vuong-function into text:
vuong2 <- deparse(vuong)
# remove the current return statement:
vuong2 <- vuong2[!grepl("return", vuong2)]
# instead of printing the output, return it!:
vuong2 <- gsub("print(out)", "return(out)", vuong2, fixed = T)
# now change the text back into an actual function that can be called:
vuong2 <- eval(parse(text = vuong2))

# Now fit some example models to test the modified function:
data("bioChemists", package = "pscl")
fm_zip <- zeroinfl(art ~ . | 1, data = bioChemists)
fm_zinb <- zeroinfl(art ~ . | 1, data = bioChemists, dist = "negbin")

# Test the modified function. Look it returns the test results... Nice...
result <- vuong2(fm_zip, fm_zinb)

print(result)