R Error in ：missing values are not allowed in subscripted assignments of data frames

模拟报错发生：

#生成一个data.frame
set.seed(0)
data <- data.frame(x=c(NA, rnorm(99)), y=c(1:5))
head(data)

生成一个6x2的data.frame，包含一个NA值， 

 ,

#将data.frame中小于0的值替换为0
data[data$x<0,]$x <- 0

报错发生了： 

Error in `[<-.data.frame`(`*tmp*`, data$x < 0, , value = list(x = c(0,  : 
  missing values are not allowed in subscripted assignments of data frames

报错很明显，da