Advanced Data Structures

Lookup Table

Map Keys to Values

Named vectors are compact lookup tables when every value has the same type.

Program

Play the script to choose a key and retrieve the mapped status code.

lookup_table.R 
key_index <- 
codes <- c(ok = 200, missing = 404, error = 500)
key <- c("ok", "missing", "error")[key_index]
value <- codes[[key]]
label <- paste(key, value, sep = ":")
cat(label, "\n", sep = "")

key_index <- 
codes <- c(ok = 200, missing = 404, error = 500)
key <- c("ok", "missing", "error")[key_index]
value <- codes[[key]]
label <- paste(key, value, sep = ":")
cat(label, "\n", sep = "")

key_index <- 
codes <- c(ok = 200, missing = 404, error = 500)
key <- c("ok", "missing", "error")[key_index]
value <- codes[[key]]
label <- paste(key, value, sep = ":")
cat(label, "\n", sep = "")
named vector A named vector maps character keys to same-type values.
lookup `codes[[key]]` retrieves the value for a selected key.
map result The final label checks both the key and returned value.