This is a simple wrapper to the match
function.
lookup(x, key, value, nomatch = NA)
x | Vector of items to lookup in key-value pairs. |
---|---|
key | Vector of keys that are searched. |
value | Vector of values to be returned. |
nomatch | The value to be returned in the case when no match is found. Note that it is coerced to integer. |
A vector the same length as x
, but containing the values
of value
. If x[i]
is equal to key[j]
, then the
value returned in the ith position of the vector is value[j]
.
If no match is found, NA
is returned.
Search for elements of x
in key
and return the corresponding
element of value
.
If no match is found, return nomatch
.
Kevin Wright
# Example 1. A and B have different factor levels A <- factor(c("A","E","F")) B <- factor(c("E","F","G")) v <- c(4,2,0) lookup(A,B,v)#> [1] NA 4 2# Example 2. Merge treatment means back into the raw data dat <- data.frame(Trt = rep(LETTERS[1:5],2), x=round(rnorm(10),2)) # Treatment B is missing all values, treatment D missing one value dat$x[dat$Trt=="B"] <- NA dat$x[4] <- NA # Calculate treatment means TrtMean <- tapply(dat$x, dat$Trt, mean, na.rm=TRUE) TrtMean#> A B C D E #> -0.125 NaN -1.345 -0.240 0.170