How to selectively sum rows [Beginner question]
It would be good to follow the posting guide and at least supply a sample of the data. Most likely 'tapply' is one way of doing it: tapply(df$passenger, list(df$orig, df$dest), sum)
On Mon, Oct 24, 2011 at 11:27 AM, asindc <siirilaa at eastwestcenter.org> wrote:
Hi, I am new to R so I would appreciate any help. I have some data that has passenger flight data between city pairs. The way I got the data, there are multiple rows of data for each city pair; the number of passengers needs to be summed to get a TOTAL annual passenger count for each city pair. So my question is: how do I create a new table (or data frame) that selectively sums My initial thought would be to iterate through each row with the following logic: 1. If the ORIGIN_WAC and DEST_WAC pair are not in the new table, then add them to the table 2. If the ORIGIN_WAC and DEST_WAC pair already exist, then sum the passengers (and do not add a new row) Is this logical? If so, I think I just need some help on syntax (or do I use a script?). Thanks. The first few rows of data look like this: -- View this message in context: http://r.789695.n4.nabble.com/How-to-selectively-sum-rows-Beginner-question-tp3933512p3933512.html Sent from the R help mailing list archive at Nabble.com.
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Jim Holtman Data Munger Guru What is the problem that you are trying to solve?