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11. Set Functions

These functions manipulate arrays and lists as sets.

11.1 complement

Synopsis

Extract the elements of a set that are not contained in other sets.

Usage

indices = complement (a, b, ..., c)

Description

This function computes the elements of the first argument (a) that are not contained in the sets given by the other arguments (b,...,c) and returns them in the form of indices into the first argument.

Example

   a = {"foo", PI, 7};
   b = [1,2,3,PI];
   indices = complement (a, b);
Upon return, indices will have the value [0, 2] since a[0] and a[2] are not contained in b.

Notes

A set may either be an Array_Type or a List_Type object. For a homogeneous collection of objects, it is better to use an Array_Type. i.e., [1,2,3] instead of {1,2,3}.

See Also

intersection, ismember, union, unique

11.2 intersection

Synopsis

Extract the common elements of two or more sets

Usage

indices = complement (a, b, ..., c)

Description

This function computes the common elements of two or more sets and returns them in the form of indices into the first argument.

Example

   a = {"foo", 7, PI};
   b = {PI, "bar", "foo"};
   indices = intersection (a, b);
Upon return, indices will have the value [0, 2] since a[0] and a[2] are the common elements of the sets.

Notes

A set may either be an Array_Type or a List_Type object. For a homogeneous collection of objects, it is better to use an Array_Type. i.e., [1,2,3] instead of {1,2,3}.

See Also

complement, ismember, union, unique

11.3 ismember

Synopsis

test to see if the elements of one set are members of another

Usage

val = ismember (a, b)

Description

This function may be used to see which of the elements of the set a are members of the set b. It returns a boolean array indicating whether or not the corresponding element of a is a member of b.

Notes

A set may either be an Array_Type or a List_Type object. For a homogeneous collection of objects, it is better to use an Array_Type. i.e., [1,2,3] instead of {1,2,3}.

See Also

complement, intersection, union, unique

11.4 union

Synopsis

Form a set of the unique elements of one ore more subsets

Usage

abc = union (a, b,..., c)

Description

This function interprets each of its arguments as a set, then merges them together and returns only the unique elements. The returned value may either be an Array_Type or a List_Type object.

Notes

A set may either be an Array_Type or a List_Type object. For a homogeneous collection of objects, it is better to use an Array_Type. i.e., [1,2,3] instead of {1,2,3}.

See Also

complement, intersection, ismember, unique

11.5 unique

Synopsis

Get the indices of the unique elements of a set

Usage

indices = unique (A)

Description

This function returns an array of the indices of the unique elements of a set.

Notes

A set may either be an Array_Type or a List_Type object. For a homogeneous collection of objects, it is better to use an Array_Type. i.e., [1,2,3] instead of {1,2,3}.

See Also

complement, intersection, ismember, union


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