00schneider - 3 months ago 27

R Question

I am an R beginner. I would like to trim a variable using the Trim function of the package "DescTools". This works fine with:

`mydata <- data.frame(`

a <- rnorm(40, mean = 0, sd = 1)

)

a_trim <- Trim(mydata$a, trim = 0.2, na.rm = TRUE)

This creates an object, however, I would like to add it to my dataframe mydata. When I try to do this by

`mydata$a_trim <- Trim(mydata$a, trim = 0.2, na.rm = TRUE)`

R gives me an error because mydata$a_trim has fewer rows than the dataframe (obviously, since it is a trimmed variable). How can I do this?

Thanks for your patience and help!

Answer

`Trim`

isn't suitable for what you want to do. It *removes* extreme values from a vector so that you can pass that vector to something like `mean`

or `sd`

so that those quantities can be computed without the influence of outliers.

To set extreme values to NA you can use `quantile`

.

```
upper_quantile <- quantile(mydata$a, 0.9)
lower_quantile <- quantile(mydata$a, 0.1)
# col a where a > its 90th percentile becomes NA
mydata$a[mydata$a > upper_quantile] <- NA
mydata$a[mydata$a < lower_quantile] <- NA
```