Remap values in a set of columns.

map_column_values(source, colmap, ..., null_default = FALSE)

Arguments

source

optree relop node or data.frame.

colmap

data.frame with columns column_name, old_value, new_value.

...

force later arguments to bind by name.

null_default

logical, if TRUE map non-matching values to NULL (else they map to self).

Value

implementing optree or altered data.frame

Examples

if (requireNamespace("DBI", quietly = TRUE) && requireNamespace("RSQLite", quietly = TRUE)) { my_db <- DBI::dbConnect(RSQLite::SQLite(), ":memory:") d <- rq_copy_to(my_db, 'd', data.frame(a = c("1", "2", "1", "3"), b = c("1", "1", "3", "2"), c = c("1", "2", "3", "4"), stringsAsFactors = FALSE), temporary = TRUE, overwrite = TRUE) mp <- build_frame( "column_name", "old_value", "new_value" | "a" , "1" , "10" | "a" , "2" , "20" | "b" , "1" , "100" | "b" , "3" , "300" ) # example op_tree <- d %.>% map_column_values(., mp) cat(format(op_tree)) sql <- to_sql(op_tree, my_db) cat(sql) print(DBI::dbGetQuery(my_db, sql)) # cleanup DBI::dbDisconnect(my_db) }
#> mk_td("d", c( #> "a", #> "b", #> "c")) %.>% #> sql_node(., #> map_column_values(., mp)) #> SELECT #> CASE WHEN `a` = '1' THEN '10' WHEN `a` = '2' THEN '20' ELSE `a` END AS `a`, #> CASE WHEN `b` = '1' THEN '100' WHEN `b` = '3' THEN '300' ELSE `b` END AS `b`, #> `c` AS `c` #> FROM ( #> SELECT #> `a`, #> `b`, #> `c` #> FROM #> `d` #> ) tsql_30551502190924422489_0000000000 #> a b c #> 1 10 100 1 #> 2 20 100 2 #> 3 10 300 3 #> 4 3 2 4