Sorry, I attempted to paste the sample data but it must have been stripped out when I posted. It is hopefully now listed below.
tapply looks useful. I will check it out further. Here's the sample data: > flights[1:10,] PASSENGERS DISTANCE ORIGIN ORIGIN_CITY_NAME ORIGIN_WAC DEST DEST_CITY_NAME DEST_WAC YEAR 1 17266 5995 LAX Los Angeles, CA 91 ICN Seoul, South Korea 778 2010 2 16934 5995 LAX Los Angeles, CA 91 ICN Seoul, South Korea 778 2010 3 15470 5995 LAX Los Angeles, CA 91 ICN Seoul, South Korea 778 2010 4 13997 5995 ICN Seoul, South Korea 778 LAX Los Angeles, CA 91 2010 5 13738 5995 LAX Los Angeles, CA 91 ICN Seoul, South Korea 778 2010 6 13682 5995 LAX Los Angeles, CA 91 ICN Seoul, South Korea 778 2010 7 13187 5995 ICN Seoul, South Korea 778 LAX Los Angeles, CA 91 2010 8 13051 5995 LAX Los Angeles, CA 91 ICN Seoul, South Korea 778 2010 9 12761 1940 SPN Saipan, TT 5 ICN Seoul, South Korea 778 2010 10 12419 5995 ICN Seoul, South Korea 778 LAX Los Angeles, CA 91 2010 Thanks, Aaron -----Original Message----- From: jim holtman [mailto:jholt...@gmail.com] Sent: Monday, October 24, 2011 11:58 AM To: asindc Cc: r-help@r-project.org Subject: Re: [R] 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 <siiri...@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. > > ______________________________________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. > -- Jim Holtman Data Munger Guru What is the problem that you are trying to solve? ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
