Às 10:52 de 20/01/2026, Eric Berger escreveu:
Here is one approach with base R, starting with your first 2 lines, then a 1-linerdf1 = data.frame(x = 1:20, y = rep(letters[1:5],4), w = c(rep(LETTERS[1],10), rep(LETTERS[2],10)), z = rnorm(20), stringsAsFactors = FALSE) df2 = data.frame(x = sample(df1$x, 5)) df2 <- merge(df2, df1, by="x", sort=FALSE)[,c("x","z")] HTH, Eric On Tue, Jan 20, 2026 at 12:25 PM Luigi Marongiu <[email protected]> wrote:Dear all, this is a basic question but I could not find a specific answer online. I have a dataframe (df1) with, in particular, an identification value `x` and an output value `z`. I also have another dataframe (df2) that shares `x`. I need to assign `z` to df2 where df1$x is equal to df2$x. What would be a straightforward way of doing this? I can do it, but selecting one element at a time, checking the identity of the x elements, and then assigning z. There should be a more R way... Thank you ``` df1 = data.frame(x = 1:20, y = rep(letters[1:5],4), w = c(rep(LETTERS[1],10), rep(LETTERS[2],10)), z = rnorm(20), stringsAsFactors = FALSE) df2 = data.frame(x = sample(df1$x, 5)) df2$z = NA for (i in df1$x) { df2$z[df2$x==i] = df1[df1$x==i,]$z } ``` ______________________________________________ [email protected] 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.______________________________________________ [email protected] 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.
Hello, Another option is i <- match(df2$x, df1$x) df2$z <- df1$z[i] or simply df2$z <- df1$z[match(df2$x, df1$x)] Hope this helps, Rui Barradas ______________________________________________ [email protected] 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.
