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Matching a pattern with `match()` with extra condition

Expanding on a previous question ( R: gsub of exact full string with fixed = T ). [With huge thanks to everyone who helped there. Special thanks to @MrFlick]

I need to change "32 oz" to "32 ct" but only if extra condition "3" is met, not in any other case.

exact_orig   = c("oz"   ,"32 oz")
exact_change = c("20 oz","32 ct")
exact_flag   = c("1"    ,"3")

fixedTrue<-function(x,y) {
  m <- match(x, exact_orig)
  n <- match(y, exact_flag)
  x[!is.na(m) & n[!is.na(n)]]<- exact_change[m[!is.na(m)] & n[!is.na(n)]]
  x
}

print(fixedTrue(c("32 oz","oz oz","32 oz", "oz", "oz"),c("1","1","3","1","2")))

Result:

[1] "20 oz" "oz oz" "32 ct" NA      NA  

Desired output:

[1] "32 oz" "oz oz" "32 ct" "20 oz" "oz"

Edit: tried the following

  x[!is.na(m&n)]<- exact_change[m[!is.na(m&n)]]

  print(fixedTrue(c("32 oz","oz oz","32 oz", "oz", "oz"),c("1","1","3","1","3")))

Got:

[1] "32 ct" "oz oz" "32 ct" "20 oz" "20 oz"

I don't see how first "32 oz" changes to "32 ct" if the flag in test case is "1" not "3"

This works:

fixedTrue <- function(x, y) {
   toChange <- which(match(x, exact_orig) == match(y, exact_flag))
   x[toChange] <- exact_change[match(x[toChange], exact_orig)]
}

Amended to check positions in flag and orig the same

Slightly closer to original:

fixedTrue <- function(x, y) {
  m <- match(x, exact_orig); n <- match(y, exact_flag)
  x[which(m == n)] <- exact_change[m[which(m == n)]]
}

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