Replace a string from lookuptable in R - r

Question

I have a txt file with a list:
name
Test_123
run_456
Test_789
I have another lookuptable that contains the "ID" and gives me a "Plate"
ID plate
123 xxx
456 zzz
789 bbb
Would love to get here
Test_xxx
run_zzz
Test_bbb
My current code does not work entirely.
Either getting <NA> as I guess it looks for values and not for a string or errors.
Thanks so much for your help!
B

Answer 1

A tidyverse way to do this would be:
library(tidyverse)
df1 %>%
separate(name, c("name", "ID"), convert=TRUE) %>%
left_join(df2, by="ID") %>%
mutate(new_name = paste(name, plate, sep="_"))
Using:
df1 <- structure(list(name = c("Test_123", "run_456", "Test_789")),
.Names = "name", class = "data.frame", row.names = c(NA, -3L))
df2 <- structure(list(ID = c(123L, 456L, 789L), plate = c("xxx", "zzz",
"bbb")), .Names = c("ID", "plate"), class = "data.frame", row.names = c(NA,
-3L))
Note that:
separate(..., convert=TRUE) use some heuristics to convert character into integer. You can otherwise do this manually: mutate(ID=as.integer(ID))
You could use unite() (which does the opposite of separate()) instead of mutate(new_name = paste(name, plate, sep="_")), which would also remove the previous columns

Answer 2

An option would be gsubfn
library(gsubfn)
gsubfn("(\\d+)", setNames(as.list(df2$plate), df2$ID), df1$name)
#[1] "Test_xxx" "run_zzz" "Test_bbb"
data
df1 <- structure(list(name = c("Test_123", "run_456", "Test_789")),
.Names = "name", class = "data.frame", row.names = c(NA, -3L))
df2 <- structure(list(ID = c(123L, 456L, 789L), plate = c("xxx", "zzz",
"bbb")), .Names = c("ID", "plate"), class = "data.frame", row.names = c(NA,
-3L))

Answer 3

For a base R option, you could add a new column to your first data frame with the exact join data:
df1$ID <- sub(".*_(?=[0-9]+)", "", df1$name, perl=TRUE)
df1$start <- sub("_[0-9]+", "", df1$name)
Then, use merge:
result <- merge(df1, df2, by="ID")
And finally create your desired output column:
result$out <- paste0(result$start, "_", result$plate)
result$out
[1] "Test_xxx" "run_zzz" "Test_bbb"
Data:
df1 <- data.frame(name=c("Test_123", "run_456", "Test_789"), stringsAsFactors=FALSE)
df2 <- data.frame(ID=c("123", "456", "789"),
plate=c("xxx", "zzz", "bbb"), stringsAsFactors=FALSE)
Demo