# R: Count number of objects in list

## R: Count number of objects in list

Get or set the length of vectors (including lists) and factors, and of any other R object for which a method has been defined.

Get the length of each element of a list or atomic vector (is.atomic) as an integer or numeric vector.

Advice for `R`

newcomers like me : beware, the following is a list of **a single object** :

```
> mylist <- list (1:10)
> length (mylist)
[1] 1
```

In such a case you are not looking for the length of the list, but of its first element :

```
> length (mylist[[1]])
[1] 10
```

This is a true list :

```
> mylist <- list(1:10, rnorm(25), letters[1:3])
> length (mylist)
[1] 3
```

Also, it seems that `R`

considers a data.frame as a list :

```
> df <- data.frame (matrix(0, ncol = 30, nrow = 2))
> typeof (df)
[1] list
```

In such a case you may be interested in `ncol()`

and `nrow()`

rather than `length()`

:

```
> ncol (df)
[1] 30
> nrow (df)
[1] 2
```

Though `length()`

will also work (but its a trick when your data.frame has only one column) :

```
> length (df)
[1] 30
> length (df[[1]])
[1] 2
```

#### R: Count number of objects in list

I spent ages trying to figure this out but it is simple! You can use `length(·)`

. `length(mylist)`

will tell you the number of objects `mylist`

contains.

… and just realised someone had already answered this- sorry!