mergeAttr: Merge Two Data Frames and maintain variable attributes
In eatModel: Educational Assessment Tools for IRT Modeling using Conquest or TAM

Description Usage Arguments Value Author(s) Examples

This is a wrapper for the merge function from the base package. merge does not maintain variable attributes. mergeAttr might be useful if variable attributes should be maintained.

mergeAttr(x, y, by = intersect(names(x), names(y)),
      by.x = by, by.y = by, all = FALSE, all.x = all, all.y = all,
      sort = TRUE, suffixes = c(".x",".y"), setAttr = TRUE, onlyVarValLabs = TRUE,
      homoClass = TRUE)

`x`	first data frame to be merged.
`y`	second data frame to be merged.
`by`	specifications of the columns used for merging
`by.x`	specifications of the columns used for merging
`by.y`	specifications of the columns used for merging
`all`	logical; `all = L` is shorthand for `all.x = L` and `all.y = L`, where `L` is either `TRUE` or `FALSE`.
`all.x`	logical; if `TRUE`, then extra rows will be added to the output, one for each row in `x` that has no matching row in `y`. These rows will have `NAs` in those columns that are usually filled with values from `y`. The default is `FALSE`, so that only rows with data from both `x` and `y` are included in the output.
`all.y`	logical; analogous to `all.x`.
`sort`	logical. Should the result be sorted on the `by` columns?
`suffixes`	a character vector of length 2 specifying the suffixes to be used for making unique the names of columns in the result which not used for merging (appearing in `by` etc).
`setAttr`	Logical: restore the variable attributes? If FALSE, the behavior of `mergeAttr` equals the behavior of `merge`.
`onlyVarValLabs`	Logical: If TRUE, only the variable and value labels will be restored. If FALSE, all variable attributes will be restored.
`homoClass`	Logical: Beginning with R version 3.5, `merge` may give an error if the class of the by-variables differs in both data.frames. If TRUE, class of by-variable(s) will be homogenized before merging.

data frame. See the help page of merge for further details.

Sebastian Weirich

### data frame 1, variable 'y' with variable.label 'test participation'
df1 <- data.frame ( id = 1:3, sex = factor ( c("male", "male", "female")), y = c(TRUE,FALSE,FALSE))
attr(df1[,"y"], "variable.label") <- "test participation"

### data frame 2 without labels 
df2 <- data.frame ( id = c(2,4), status = factor ( c("married", "single")), z = c(TRUE,FALSE))

### lost label after merging
df3 <- merge(df1, df2, all = TRUE)
attr(df3[,"y"], "variable.label")

### maintain label
df4 <- mergeAttr(df1, df2, all = TRUE, onlyVarValLabs = FALSE)
attr(df4[,"y"], "variable.label")