scidb (version 1.1-2)

index_lookup: index_lookup

Description

The index_lookup function is a wrapper to the SciDB `index_lookup` operator. It produces a new SciDB array that joins the unqiue indices defined in the array I with values looked up in array X for attribute attr. Use the index_lookup with the unique and sort functions.

Usage

index_lookup(X, I, attr, new_attr, eval=FALSE)

Arguments

X

A scidb or scidbdf object

I

A scidb or scidbdf object

attr

A character string attribute name from the X array

new_attr

An optional character name for the new attribute, defaults to attr + "_index"

eval

(Optional) If true, execute the query and store the reult array. Otherwise defer evaluation.

Value

• A scidb or scidbdf object.

See Also

scidb

Examples

data("iris")
x <- as.scidb(iris)

# Create a unique list of elements of the "Species" attribute.
# Note that we choose to defer evaluation of this expression.
y <- unique(sort(project(x,"Species")), eval=FALSE)

# Append a new attribute to the array x called "Species_index" that
# enumerates the unique values of the "Species" attribute:
z <- index_lookup(x, y, "Species", eval=FALSE)

print(head(z))