counting duplication

[Lauren Hodgson]

Hi all,

Fastest way to find number of times a number is duplicated in a column
of a data frame???

Hint: it's not running a for loop that iterates through 30 000 unique
values of the duplicates, lol.

It's like a horrible game - answer before my stupid loop completes.


Not the answer:

duplicates=mydata$values.with.duplicates[duplicated(mydata$values.with.duplicates)]

mydata$times.duplicated=1

for (dup in duplicates) {
tt=length(mydata$values.with.duplicates[which(mydata$values.with.duplicates==dup)])
mydata$times.duplicated[which(mydata$values.with.duplicates==dup)]=tt
}

[Keith, Sally]

table(mydata$columnname)

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[Lauren Hodgson]

hahaha, awesome! thanks so much.

as.data.frame(table(mydata$columnname)) allows me to merge this info
to the main data frame.