`groupfilter`

Keeps only the rows of groups that satisfy a condition.

Category: Language Fundamentals > Data Types

Syntax

B = groupfilter(T, groupvars, fun)

Applies fun to the data of each group and keeps the groups for which it returns true.

B = groupfilter(T, groupvars, fun, datavars)

Passes only the listed data variables to fun.

Description

This is a filter at the group level. For example, groupfilter(T, 'g', @(x) numel(x) > 1, 'v') drops every group that has a single row. The test sees the whole group at once, which is what separates it from logical indexing on single rows.

Input arguments

T: Table.
groupvars: Variable(s) that define the groups.
fun: Function handle receiving the group's values and returning a logical scalar, or a logical vector with one entry per row.
datavars: Variable(s) given to fun.

Output arguments

B: Table with the rows of the groups that passed, in original order.

Example

Dropping small groups

tb = table(categorical({'a'; 'b'; 'a'; 'c'; 'a'}), [1; 2; 3; 4; 5], 'VariableNames', {'g', 'v'});
groupfilter(tb, 'g', @(x) numel(x) > 1, 'v')

Output

ans = 3×2 table

    g    v
    _    _

    a    1
    a    3
    a    5

groupfilter