R gives error with the mean but not with median

[DesperateStudet]

Good morning,
I am new and not a native-speaker, so sorry for errors. I have used this command to calculate the mean
mean(reporttb$no2,na.rm=TRUE)
but I got this error
The variable is not numeric nor logical
The weird thing is when i try to calculate the median instead, it gives me back a number without any problem. How is it possible?

[JackDavison]

Welcome to RStudio Community.

For us to diagnose your problem, we'll need a reproducible example. Please read this article for how to make one:

FAQ: What's a reproducible example (reprex) and how do I create one?

A quick way of doing this is to provide us the output of dput(reporttb) or, if its very long, dput(head(reporttb, 100)).

[startz]

median() is defined for some types other than numeric. For example,

> median(c("a","c","b"))
[1] "b"

[technocrat]

@startz answer you should mark as the solution. To see more detail use help() for the two functions.

For help(mean) the argument, x

x An R object. Currently there are methods for numeric/logical vectors and date, date-time and time interval objects. Complex vectors are allowed for trim = 0, only.

That tells you that only dates and numbers can be used.

For help(median) the argument x

x an object for which a method has been defined, or a numeric vector containing the values whose median is to be computed.

is a little trickier. You can use numbers, it clearly says, but what is "an object for which a method has been defined?"

That's a bit of R geekery, which means that the default can be modified by a "method." But the interesting part is in Details

the default method will work for most classes (e.g., "Date") for which a median is a reasonable concept.

Why are characters a reasonable concept? Because they are ordered. a is less than c and c is less than a. For example:

 > letters[c(1,3,2)]
   #[1] "a" "c" "b"

the number being used is an integer index.

Note, however, that this works only for an odd number of arguments.

> median("a","c","b","d")
Error in if (na.rm) x <- x[!is.na(x)] else if (any(is.na(x))) return(x[FALSE][NA]) : argument is not interpretable as logical

because you can't have half an index.