lookup: Data Key Lookup
In patperry/r-frame: Flexible Data Frames

Description Usage Arguments Details Value See Also Examples

Find rows with specified keys.

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lookup(x, table, default = NA)

rowid(table, x, default = NA)

`x`	the values to be matched.
`table`	the values to be matched against.
`default`	the value to return when no row in the `table` matches.

The lookup and rowid functions to the same thing, but have their arguments transposed. Each finds the corresponding entry in the table for each entry in x; for values in x with no match, return the default value.

The rowid function is generic. The default implementation converts table with as.keyset and converts x with as.dataset, then finds the rows in the table corresponding to the rows in x.

The lookup function calls the rowid generic.

A vector of row indices in table for the corresponding rows in the x argument. Rows with no match get the default value (converted to numeric).

keyset, match.

# look up single-component keys
table <- keyset(name = rownames(mtcars))
lookup(c("Valiant", "Fiat 128", "Delorean"), table)

# rowid returns the same result but has its arguments swapped
rowid(table, c("Valiant", "Fiat 128", "Delorean"))

# multi-component keys
keys <- keyset(k1 = rep(LETTERS[1:4], each = 8), k2 = rep(1:8, 4))

# look up a single item
lookup(record(k1 = "A", k2 = 5), keys)

# look up multiple items
lookup(dataset(k1 = c("A", "A", "B", "Z"),
               k2 = c(  5, 100,   1,   3)), keys)