Replace entire strings based on partial match - regex

Question

New to R. Looking to replace the entire string if there is a partial match.
d = c("SDS0G2 Blue", "Blue SSC2CWA3", "Blue SA2M1GC", "SA5 Blue CSQ5")
gsub("Blue", "Red", d, ignore.case = FALSE, fixed = FALSE)
Output: "SDS0G2 Red" "Red SSC2CWA3" "Red SA2M1GC" "SA5 Red CSQ5"
Desired Output: “Red” “Red” “Red” “Red”
Any help in solving this is truly appreciated.

Answer 1

I'd suggest using grepl to find the indices and replace those indices with "Red":
d = c("SDS0G2 Blue", "Blue SSC2CWA3", "Blue SA2M1GC", "SA5 Blue CSQ5", "ABCDE")
d[grepl("Blue", d, ignore.case=FALSE)] <- "Red"
d
# [1] "Red" "Red" "Red" "Red" "ABCDE"

Answer 2

If you did want to keep the variable as a factor and replace multiple partial matches at once, the following function will work (example from another question).
clrs <- c("blue", "light blue", "red", "rose", "ruby", "yellow", "green", "black", "brown", "royal blue")
dfx <- data.frame(colors1=clrs, colors2 = clrs, Amount=sample(100,10))
# Function to replace levels with regex matching
make_levels <- function(.f, patterns, replacement = NULL, ignore.case = FALSE) {
lvls <- levels(.f)
# Replacements can be listed in the replacement argument, taken as names in patterns, or the patterns themselves.
if(is.null(replacement)) {
if(is.null(names(patterns)))
replacement <- patterns
else
replacement <- names(patterns)
}
# Find matching levels
lvl_match <- setNames(vector("list", length = length(patterns)), replacement)
for(i in seq_along(patterns))
lvl_match[[replacement[i]]] <- grep(patterns[i], lvls, ignore.case = ignore.case, value = TRUE)
# Append other non-matching levels
lvl_other <- setdiff(lvls, unlist(lvl_match))
lvl_all <- append(
lvl_match,
setNames(as.list(lvl_other), lvl_other)
)
return(lvl_all)
}
# Replace levels
levels(dfx$colors2) <- make_levels(.f = dfx$colors2, patterns = c(Blue = "blue", Red = "red|rose|ruby"))
dfx
#> colors1 colors2 Amount
#> 1 blue Blue 75
#> 2 light blue Blue 55
#> 3 red Red 47
#> 4 rose Red 83
#> 5 ruby Red 56
#> 6 yellow yellow 10
#> 7 green green 25
#> 8 black black 29
#> 9 brown brown 23
#> 10 royal blue Blue 24
Created on 2020-04-18 by the reprex package (v0.3.0)