Filling up a table in R

Question

I've got 2 vectors:

c1 <- c(1,2,0,1,3,4,5,6,1,2,3,0)
c2 <- c(1,2,0,5,0,2,1)

> table(c1)   
c1   
0 1 2 3 4 5 6   
2 3 2 2 1 1 1   
> table(c2)  
c2  
0 1 2 5   
2 2 2 1

Now I want c2 to have the following form:

> table(c2)  
c2  
0 1 2 3 4 5 6   
2 2 2 0 0 1 0

How can I get out of these tables the vectors (2, 3, 2, 2, 1, 1, 1) and (2, 2, 2, 0, 0, 1, 0)?

See also [**this**](http://stackoverflow.com/questions/19773435/how-can-you-force-inclusion-of-a-level-in-a-table-in-r/19773510#19773510) or [**this**](http://stackoverflow.com/questions/1617061/including-absent-values-in-table-results-in-r/1617150#1617150). — Henrik, Nov 06 '14 at 14:48

score 4 · Accepted Answer · answered Nov 06 '14 at 14:21

So R doesn't know that there are missing values. The easiest way to convince it of this is to specify that the levels of the factor include missing elements.

For example

> table(factor(c2, levels=0:6))

0 1 2 3 4 5 6
2 2 2 0 0 1 0

For the second part of this question, usually the table itself is adequate for most purposes.

> a <- table(factor(c2, levels=0:6))
> a[1] + 1
0
3

if you ignore the "0" header, then you can do almost any vector manipulation. But if you want to remove the headers completely, you can convert to a raw numeric array

> as.numeric(a)
[1] 2 2 2 0 0 1 0

I think the OP wanted levels corresponding to `c1` rather than setting them manually — David Arenburg, Nov 06 '14 at 14:23

David Arenburg · Answer 2 · 2014-11-06T14:44:27.497

Use factor and pass unique values of c1 to levels of c2 in order to set empty entries corresponding to c1 values

table(factor(c2, levels = sort(unique(c1))))
# 0 1 2 3 4 5 6 
# 2 2 2 0 0 1 0

Or use union (as mentioned in @Svens deleted answer)

table(factor(c2, levels = sort(union(c1, c2))))
# 0 1 2 3 4 5 6 
# 2 2 2 0 0 1 0

In order to get the actual values use as.numeric

as.numeric(table(factor(c2, levels = sort(unique(c1)))))
## [1] 2 2 2 0 0 1 0

Filling up a table in R

2 Answers2