Question

I have a single column in a data frame in R that looks something like this:

blue
green
blue
yellow
black
blue
green

How do I remove all the rows that indicate blue? Please keep in mind that I don’t want a NULL value represented in that row: I want the entire row removed.

Thank you 🙂

Answer 1

Also be careful about the difference between a factor variable and character vector.

Factors retain all original levels by default unless you reassign the altered vector as a new factor, or use one of the relevel functions.

> DF <- data.frame(v = factor(c("red", "blue", "green", "blue")))
> summary(DF)
     v    
 blue :2  
 green:1  
 red  :1  
> summary(DF[ DF$v != "blue", , drop=FALSE])
     v    
 blue :0  
 green:1  
 red  :1  
> DF <- DF[ DF$v != "blue", , drop=FALSE]; DF$v <- factor(DF$v); summary(DF)
     v    
 green:1  
 red  :1  
>