Naresh Gurbuxani
2025-Sep-18 14:10 UTC
[R] Fwd: Matching when each subject has multiple records
?> mydf <- data.frame(date = as.Date("2010-01-01") + sample(500, size = 20), subject = sample(c("A", "B", "C"), 20, replace = TRUE), first = FALSE) > mydf <- mydf[order(mydf$date),] > df_split <- split(mydf, f = mydf$subject) > df_split <- lapply(df_split, function(df) {df[1, "first"] <- TRUE; df}) > mydf <- do.call(rbind, df_split)[[alternative HTML version deleted]]
Naresh, I appreciate your reply. In my original posting, I neglected to mention that I want to propensity score match the two groups. I don't think you suggestion will help me propensity score match my data. Am I missing something? Thank you, 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 ________________________________________ From: R-help <r-help-bounces at r-project.org> on behalf of Naresh Gurbuxani <naresh_gurbuxani at hotmail.com> Sent: Thursday, September 18, 2025 10:10 AM To: r-help at r-project.org <r-help at r-project.org> Subject: [R] Fwd: Matching when each subject has multiple records ?> mydf <- data.frame(date = as.Date("2010-01-01") + sample(500, size = 20), subject = sample(c("A", "B", "C"), 20, replace = TRUE), first = FALSE) > mydf <- mydf[order(mydf$date),] > df_split <- split(mydf, f = mydf$subject) > df_split <- lapply(df_split, function(df) {df[1, "first"] <- TRUE; df}) > mydf <- do.call(rbind, df_split)[[alternative HTML version deleted]] ______________________________________________ R-help at 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.