cousera r programming 第二周作业
我的程序如下：
pollutantmean <- function(directory, pollutant, id = 1:332) {
directory<-"D:\\specdata"
files <- dir(directory, pattern="*.csv", full.names=T)
data<-data.frame()
for (i in id){
data<-rbind(data,read.csv(files),header=TRUE)
}
if (pollutant == "sulfate") {
mean <- mean(data$sulfate, na.rm = TRUE)
}
if (pollutant == "nitrate") {
mean <- mean(data$nitrate, na.rm = TRUE)
}
print(mean)
}
报错：
Warning messages:1: In `[<-.factor`(`*tmp*`, ri, value = TRUE) : invalid factor level, NA generated2: In `[<-.factor`(`*tmp*`, ri, value = TRUE) : invalid factor level, NA generated3: In `[<-.factor`(`*tmp*`, ri, value = TRUE) : invalid factor level, NA generated4: In `[<-.factor`(`*tmp*`, ri, value = TRUE) : invalid factor level, NA generated5: In `[<-.factor`(`*tmp*`, ri, value = TRUE) : invalid factor level, NA generated6: In `[<-.factor`(`*tmp*`, ri, value = TRUE) : invalid factor level, NA generated7: In `[<-.factor`(`*tmp*`, ri, value = TRUE) : invalid factor level, NA generated8: In `[<-.factor`(`*tmp*`, ri, value = TRUE) : invalid factor level, NA generated9: In `[<-.factor`(`*tmp*`, ri, value = TRUE) : invalid factor level, NA generated10: In `[<-.factor`(`*tmp*`, ri, value = TRUE) : invalid factor level, NA generated
这个是哪行有问题？？
谢谢
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