Check whether two factors are crossed or nested

Description

These functions checks whether two factors are crossed or nested, i.e. if each level of one factor occurs in combination with each level of the other factor (is_crossed()) resp. if each category of the first factor co-occurs with only one category of the other (is_nested()).

Usage

is_crossed(f1, f2)

is_nested(f1, f2)

Arguments

Value

Logical. For is_crossed(), TRUE if factors are crossed, FALSE otherwise. For nested(), TRUE if factors are nested, FALSE otherwise.

Note

If factors are nested, a message is displayed to tell whether f1 is nested within f2 or vice versa.

References

Grace, K. The Difference Between Crossed and Nested Factors. (web)

Examples

# crossed factors, each category of
# x appears in each category of y
x <- c(1,4,3,2,3,2,1,4)
y <- c(1,1,1,2,2,1,2,2)
# show distribution
table(x, y)
# check if crossed
is_crossed(x, y)

# not crossed factors
x <- c(1,4,3,2,3,2,1,4)
y <- c(1,1,1,2,1,1,2,2)
# show distribution
table(x, y)
# check if crossed
is_crossed(x, y)


# nested factors, each category of
# x appears in one category of y
x <- c(1,2,3,4,5,6,7,8,9)
y <- c(1,1,1,2,2,2,3,3,3)
# show distribution
table(x, y)
# check if nested
is_nested(x, y)
is_nested(y, x)

# not nested factors
x <- c(1,2,3,4,5,6,7,8,9,1,2)
y <- c(1,1,1,2,2,2,3,3,3,2,3)
# show distribution
table(x, y)
# check if nested
is_nested(x, y)
is_nested(y, x)