Add a grouping factor
This function adds a grouping factor to an existing reference grid or other
emmGrid object, such that the levels of an existing factor (call it the
reference factor) are mapped to a smaller number of levels of the new
grouping factor. The reference factor is then nested in the grouping factor.
This facilitates obtaining marginal means of the grouping factor, and
contrasts thereof.
add_grouping(object, newname, refname, newlevs)
object |
An |
newname |
Character name of grouping factor to add (different from any existing factor in the grid) |
refname |
Character name of the reference factor |
newlevs |
Character vector or factor of the same length as that of the levels for
|
A revised emmGrid object having an additional factor named
newname, and a new nesting structure refname %in% newname
By default, the levels of newname will be ordered
alphabetically. To dictate a different ordering of levels, supply
newlevs as a factor having its levels in the required order.
fiber.lm <- lm(strength ~ diameter + machine, data = fiber)
( frg <- ref_grid(fiber.lm) )
# Suppose the machines are two different brands
brands <- factor(c("FiberPro", "FiberPro", "Acme"), levels = c("FiberPro", "Acme"))
( gfrg <- add_grouping(frg, "brand", "machine", brands) )
emmeans(gfrg, "machine")
emmeans(gfrg, "brand")Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.