Oh and don't forget: #first line of code, bring dplyr into memory after that package has been installed.
library(dplyr) On Wednesday, November 27th, 2024 at 12:05 PM, Tom Woolman <twool...@ontargettek.com> wrote: > > > Check out the dplyr package, specifically the mutate function. > > # Create new column based on existing column value > > df <- df %>% mutate(FirstDay = if(ID = 2, 5)) > > > df > > > > Repeat as needed to capture all of the day/firstday combinations you want to > account for. > > Like everything else in R, there are probably at least a dozen other ways to > do this, between base R and all of the library packages available. > > > > > On Wednesday, November 27th, 2024 at 11:30 AM, Sorkin, John > jsor...@som.umaryland.edu wrote: > > > I am an old, long time SAS programmer. I need to produce R code that > > processes a dataframe in a manner that is equivalent to that produced by > > using a by statement in SAS and an if first.day statement and a retain > > statement: > > > > I want to take data (olddata) that looks like this > > ID Day > > 1 1 > > 1 1 > > 1 2 > > 1 2 > > 1 3 > > 1 3 > > 1 4 > > 1 4 > > 1 5 > > 1 5 > > 2 5 > > 2 5 > > 2 5 > > 2 6 > > 2 6 > > 2 6 > > 3 10 > > 3 10 > > > > and make it look like this: > > (withing each ID I am copying the first value of Day into a new variable, > > FirstDay, and propagating the FirstDay value through all rows that have the > > same ID: > > > > ID Day FirstDay > > 1 1 1 > > 1 1 1 > > 1 2 1 > > 1 2 1 > > 1 3 1 > > 1 3 1 > > 1 4 1 > > 1 4 1 > > 1 5 1 > > 1 5 1 > > 2 5 5 > > 2 5 5 > > 2 5 5 > > 2 6 5 > > 2 6 5 > > 2 6 5 > > 3 10 3 > > 3 10 3 > > > > SAS code that can do this is: > > > > proc sort data=olddata; > > by ID Day; > > run; > > > > data newdata; > > retain FirstDay; > > set olddata; > > by ID; > > if first.ID then FirstDay=Day; > > run; > > > > I have NO idea how to do this is R (so I can't post test-code), but below I > > have R code that creates olddata: > > > > ID <- c(rep(1,10),rep(2,6),rep(3,2)) > > date <- c(rep(1,2),rep(2,2),rep(3,2),rep(4,2),rep(5,2), > > rep(5,3),rep(6,3),rep(10,2)) > > date > > olddata <- data.frame(ID=ID,date=date) > > olddata > > > > Any suggestions on how to do this would be appreciated. . . I have worked > > on this for more than 12-hours, despite multiple we searches I have gotten > > nowhere. . . > > > > Thanks > > John > > > > John David Sorkin M.D., Ph.D. > > Professor of Medicine, University of Maryland School of Medicine; > > Associate Director for Biostatistics and Informatics, Baltimore VA Medical > > Center Geriatrics Research, Education, and Clinical Center; > > PI Biostatistics and Informatics Core, University of Maryland School of > > Medicine Claude D. Pepper Older Americans Independence Center; > > Senior Statistician University of Maryland Center for Vascular Research; > > > > Division of Gerontology and Paliative Care, > > 10 North Greene Street > > GRECC (BT/18/GR) > > Baltimore, MD 21201-1524 > > Cell phone 443-418-5382 > > > > ______________________________________________ > > R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see > > https://stat.ethz.ch/mailman/listinfo/r-help > > PLEASE do read the posting guide > > https://www.R-project.org/posting-guide.html > > and provide commented, minimal, self-contained, reproducible code. > > > ______________________________________________ > R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide https://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide https://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
