仅在将Rmarkdown编译为.pdf时才会出现此错误。当我运行我的实际R代码时，我没有错误。可重现的错误：
library(dplyr)
data <- read.table('http://data.princeton.edu/eco572/datasets/brazilDeathRates1999.dat', header = TRUE)
data <- mutate(data, n = c(diff(age), 0))
kfnax <- read.dta("http://data.princeton.edu/eco572/datasets/kfnax.dta")
data<- inner_join(data, kfnax, by="age")
data <- rename(data, a = nax) # for simplicity
data <- mutate(data, q_males = n * males/(1 + (n - a) * males), p_males = 1 - q_males)
data <- mutate(data, q_females = n * females/(1 + (n - a) * females), p_females = 1 - q_females)
#makes the last values 1 and 0 respectively for death probability
data[last, c("q_males","p_males")] = c(1, 0)
data[last, c("q_females","p_females")] = c(1, 0)
此行似乎触发了错误：
data <- mutate(data, q_males = n * males/(1 + (n - a) * males), p_males = 1 - q_males)