在 R 中搜索和替换字符串、不匹配的模式和 NA

Question

I have character vector (column) in a data.frame that contains three correct values comprised of "Positive", "Negative" and NA, along a small number of incorrect values. I want to replace the incorrect values, ie everything except "Positive", "Negative" and "NA" with "Positive" I can grep for NOT "Positive" or "Negative", using grep and the invert=TRUE argument, and get everything except instances of "Negative" and "Positive" but I've not figured out how to additionally, not replace any instances of NA. I've also looked at the sub command, but it does not have an invert option. Any suggestions?

Answer 1

This should work:

df[!is.na(df$column) & !df$column %in% 
        c("Positive","Negative"), "column"] <- "Positive"