by including NA in " " we transform it into a real missing value in an R factor vector
```
HIV_coded$bisexual<- factor(replace(HIV_coded$bisexual, HIV_coded$bisexual == "NA", NA))
```
-
Sometimes when you are running a regression model with variables that have different lengths, r will prompt with the following error message...
-
retinol$age [1] 64 76 38 40 72 40 65 58 35 55 66 40 57 66 66 64 62 75 68 57 56 30 34 53 60 50 62 61 65 71 43 33 74 41 [35] 56 44 37 3...
