R: Extract and display information on all pairwise comparisons...

cld.emmGrid {emmeans} | R Documentation

## Extract and display information on all pairwise comparisons of least-squares means.

### Description

Extract and display information on all pairwise comparisons of least-squares means.

### Usage

    ## S3 method for class 'emmGrid'
    cld(object, details = FALSE, sort = TRUE, by,
      alpha = 0.05, Letters = c("1234567890", LETTERS, letters),
      reversed = FALSE, ...)

### Arguments

`object` | An object of class `emmGrid`
`details` | Logical value determining whether detailed information on tests of pairwise comparisons is displayed
`sort` | Logical value determining whether the EMMs are sorted before the comparisons are produced. When `TRUE`, the results are displayed according to `reversed`.
`by` | Character value giving the name or names of variables by which separate families of comparisons are tested. If NULL, all means are compared. If missing, the object's `by.vars` setting, if any, is used.
`alpha` | Numeric value giving the significance level for the comparisons
`Letters` | Character vector of letters to use in the display. Any strings of length greater than 1 are expanded into individual characters
`reversed` | Logical value (passed to `multcompView::multcompLetters`.) If `TRUE`, the order of use of the letters is reversed. In addition, if both `sort` and `reversed` are TRUE, the sort order of results is reversed.
`...` | Arguments passed to `contrast` (for example, an `adjust` method) This function uses the Piepho (2004) algorithm (as implemented in the multcompView package) to generate a compact letter display of all pairwise comparisons of least-squares means. The function obtains (possibly adjusted) P values for all pairwise comparisons of means, using the `contrast` function with `method = "pairwise"`. When a P value exceeds `alpha`, then the two means have at least one letter in common.

### Value

When details == FALSE, an object of class `summary.ref_grid` (which inherits from `data.frame`) showing the summary of EMMs with an added column named `.groups` containing the `cld` information. When `details == TRUE`, a `list` with the object just described, as well as the summary of the contrast results showing each comparison, its estimate, standard error, t ratio, and adjusted P value.

### References

Hans-Peter Piepho (2004) An algorithm for a letter-based representation of all pairwise comparisons, Journal of Computational and Graphical Statistics, 13(2), 456-466.

### See Also

`cld` in the multcomp package

### Examples

    warp.lm <- lm(breaks ~ wool * tension, data = warpbreaks)
    warp.emm <- emmeans(warp.lm, ~ tension | wool)
    cld(warp.emm)                  # implicitly uses by = "wool"
    cld(warp.emm, by = "tension")  # overrides implicit 'by'

    # Mimic grouping bars and compare all 6 means
    cld(warp.emm, by = NULL, Letters = "||||||||", alpha = .01)

[Package emmeans version 1.1.3 Index]