一列中不同观察值的数量

Question

How can I find how many different observations there are in a column? For example in a column "species" with 3000 rows I want to find how many different species there are.

I read something about str(data) but I can't find it there. Thank you in advance. (I am new in R)

Answer 1

You can use length and unique to determine for example in the iris dataset how many unique species there are in the Species column. You can use the following code:

length(unique(iris$Species))

Output:

[1] 3

So this means there are 3 unique values in the species column.