Check whether two factors are crossed or nested

These functions checks whether two factors are (fully) 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()). is_cross_classified() checks if one factor level occurs in some, but not all levels of another factor.

is_crossed(f1, f2)

is_nested(f1, f2)

is_cross_classified(f1, f2)

Arguments

f1	Numeric vector or factor.
f2	Numeric vector or factor.

Value

Logical. For is_crossed(), TRUE if factors are (fully) crossed, FALSE otherwise. For is_nested(), TRUE if factors are nested, FALSE otherwise. For is_cross_classified(), TRUE, if one factor level occurs in some, but not all levels of another factor.

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)
#>    y
#> x   1 2
#>   1 1 1
#>   2 1 1
#>   3 1 1
#>   4 1 1
# check if crossed
is_crossed(x, y)
#> [1] TRUE

# 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)
#>    y
#> x   1 2
#>   1 1 1
#>   2 1 1
#>   3 2 0
#>   4 1 1
# check if crossed
is_crossed(x, y)
#> [1] FALSE


# 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)
#>    y
#> x   1 2 3
#>   1 1 0 0
#>   2 1 0 0
#>   3 1 0 0
#>   4 0 1 0
#>   5 0 1 0
#>   6 0 1 0
#>   7 0 0 1
#>   8 0 0 1
#>   9 0 0 1
# check if nested
is_nested(x, y)
#> 'f1' is nested within 'f2'
#> [1] TRUE
is_nested(y, x)
#> 'f2' is nested within 'f1'
#> [1] TRUE

# 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)
#>    y
#> x   1 2 3
#>   1 1 1 0
#>   2 1 0 1
#>   3 1 0 0
#>   4 0 1 0
#>   5 0 1 0
#>   6 0 1 0
#>   7 0 0 1
#>   8 0 0 1
#>   9 0 0 1
# check if nested
is_nested(x, y)
#> [1] FALSE
is_nested(y, x)
#> [1] FALSE

# also not fully crossed
is_crossed(x, y)
#> [1] FALSE

# but partially crossed
is_cross_classified(x, y)
#> [1] TRUE