count {plyr} | R Documentation |
Equivalent to as.data.frame(table(x))
, but does
not include combinations with zero counts.
count(df, vars = NULL, wt_var = NULL)
df |
data frame to be processed |
vars |
variables to count unique values of |
wt_var |
optional variable to weight by - if this is non-NULL, count will sum up the value of this variable for each combination of id variables. |
Speed-wise count is competitive with table
for single variables, but it really comes into its own
when summarising multiple dimensions because it only
counts combinations that actually occur in the data.
Compared to table
+
as.data.frame
, count
also preserves
the type of the identifier variables, instead of
converting them to characters/factors.
a data frame with label and freq columns
count(baseball, "id") count(baseball, "id", "g") count(baseball, "id", "ab") count(baseball, "lg") count(baseball, "stint") count(count(baseball, c("id", "year")), "id", "freq") count(count(baseball, c("id", "year")), "freq")