on 05/23/2008 09:51 AM Economics Guy wrote:
I can think of several ways to blunt force hard code what I want but I
imagine there is a command or two that can be easily combined to do this:
I have a data frame with about 23000 observations. There first variable is
the group to which the observation belongs (about 500 different groups). The
second variable is a response for each observation that is a 1,2,3,4 or 5. I
want to be able to calculate the percentage of each group that choose each
response. For example I want to know what percentage of group 1 (which may
have a value of 34456) choose response 1 and so on.
Here is some code I wrote that generates a data frame like the one I have.
pop <- matrix(1:100000)
groupIDs <- sample(pop,500)
groupVar <- sample(groupIDs,23000,replace=TRUE)
responseVar <- sample(1:5,23000,replace=TRUE)
example.data <- data.frame(groupVar,responseVar)
Is there a fast way to calculate these percentages beyond writing loops to
manually count the responses for each of the groups?
Thanks,
EG
Using:
table(example.data)
will give you a cross tabulation of the counts of your ResponseVar by
each groupVar.
prop.table(table(example.data), 1)
will give you a row-wise proportion (0 - 1) of the counts of ResponseVar
for each groupVar. If you want percentages (0 - 100):
prop.table(table(example.data), 1) * 100
See ?table and ?prop.table for more information.
HTH,
Marc Schwartz
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