Say I have two dataframes. One is my 'main' df and the other is the one I'm using to replace values in the main df.
So in column cd
of dfMain
, every time the factor level orange
comes up I want to replace this with the corresponding row from dfReplace
(which has a rowname called orange
)
This will result in dfMain
gaining 3 columns in width because the cd
column goes away and it gains columns X1, X2, X3, X4
The key here is that I need this to be as efficient as possible because my actual data is much, much longer
Reproducible example:
set.seed(42)
dfMain <- data.frame('av' = sample.int(10, 100, replace = TRUE),
'ba' = sample.int(10, 100, replace = TRUE),
'cd' = sample(c('orange', 'apple', 'banana', 'strawberry', 'blueberry', 'blackberry'), 100, replace = TRUE))
dfReplace <- data.frame('X1' = runif(6),
'X2' = runif(6),
'X3' = runif(6),
'X4' = runif(6))
rownames(dfReplace) <- c('orange', 'apple', 'banana', 'strawberry', 'blueberry', 'blackberry')
I'd suggest first converting the rownames to an explicit table field and converting the cd factor to character, and then doing a database join, which should be very fast.
library(dplyr)
dfReplace2 <- dfReplace %>%
add_rownames(var = "cd")
dfMain %>%
mutate(cd = as.character(cd)) %>%
left_join(dfReplace2)
I left the original 'cd' field there, but could be removed with %>% select(-cd)
.
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