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# Count number of occurences for each unique value

Let's say I have:
`v = rep(c(1,2, 2, 2), 25)`

Now, I want to count the number of times each unique value appears. `unique(v)` returns what the unique values are, but not how many they are.

```> unique(v)
[1] 1 2```

I want something that gives me
```length(v[v==1])
[1] 25
length(v[v==2])
[1] 75```

but as a more general one-liner :) Something close (but not quite) like this:
`#<doesn't work right> length(v[v==unique(v)])`
by

Perhaps table is what you are after?
```dummyData = rep(c(1,2, 2, 2), 25)

table(dummyData)
# dummyData
#  1  2
# 25 75

## or another presentation of the same data
as.data.frame(table(dummyData))
#    dummyData Freq
#  1         1   25
#  2         2   75```
If you have multiple factors (= a multi-dimensional data frame), you can use the dplyr package to count unique values in each combination of factors:
```
library("dplyr")
data %>% group_by(factor1, factor2) %>% summarize(count=n())
```

It uses the pipe operator %>% to chain method calls on the data frame data.