I try to add covariates to a BT model but the estimates are all NA. Here is an example:
library(BradleyTerry2)
repex <- dplyr::tibble(
product_a = as.factor(c(1, 2, 3, 4)),
product_b = as.factor(c(4, 1, 2, 3)),
rating_a = c(1, 0, 0, 1),
rating_b = 1 - rating_a,
user = as.factor(c("aa1", "aa1", "bb2", "bb2"))
)
# This works
bt1 <- BTm(cbind(rating_a, rating_b), product_a, product_b, id = "product", formula = ~ product, data = repex)
# This doesnt (with user)
bt2 <- BTm(cbind(rating_a, rating_b), product_a, product_b, id = "product", formula = ~ product + user, data = repex)
Does someone know how to specify this model correctly to account for user biases (not player but contest specific predictors)? I tried it also with several thousands of instances but no useful estimate could be obtained. Thanks in advance for any suggestion!
Hi guys,
I try to add covariates to a BT model but the estimates are all NA. Here is an example:
Does someone know how to specify this model correctly to account for user biases (not player but contest specific predictors)? I tried it also with several thousands of instances but no useful estimate could be obtained. Thanks in advance for any suggestion!