How to extract counts as a vector from a table in R?

问题

I'm trying to write a function to extract the frequencies of this table:

 0  1  2  3  4  5  6  7
30 22  9 12  2  5  1 16

So I want to get c(30, 22, 9, 12, 2, 5, 1, 16).

The table changes each time I run the function, so I need something that can extract the information from the table automatically, so I don't have write a c() function each time.

回答1:

It honestly could not be any simpler. If you cannot figure this out, you will have lots of other problems:

> set.seed(42)                          ## be reproducible
> X <- sample(1:5, 50, replace=TRUE)    ## our data
> table(X)                              ## our table
X
 1  2  3  4  5 
 7  6  9 10 18 
> str(table(X))                         ## look at structure of object
 'table' int [1:5(1d)] 7 6 9 10 18
 - attr(*, "dimnames")=List of 1
  ..$ X: chr [1:5] "1" "2" "3" "4" ...
> as.numeric(table(X))                  ## and just convert to vector
[1]  7  6  9 10 18
> 

And for completeness, two more ways to get the data:

> unname(table(X))                      ## jdropping names reduces to the vector
[1]  7  6  9 10 18
> table(X)[]                            ## or simply access it
[1]  7  6  9 10 18
> 

来源：https://stackoverflow.com/questions/8465907/how-to-extract-counts-as-a-vector-from-a-table-in-r