Compare Two Data Frames by Key Column

Compares two data frames row-by-row based on a key column, identifying rows present in only one of the two frames and columns that differ in matched rows.

Usage

compareDataFrames(x, y, key)

Arguments

x

a data frame.

y

a data frame to compare against x.

key

character string. Name of the column used as row identifier. Must be present in both x and y, with unique values.

Value

a named list with four elements:

identical

logical. TRUE if the two data frames are identical with respect to the common columns and key.

onlyInX

data frame of rows whose key value appears in x but not in y.

onlyInY

data frame of rows whose key value appears in y but not in x.

diffs

data frame with columns named after the key argument (the key value) and diffCols (a list column of character vectors naming the differing columns for that key).

Details

Only columns present in both data frames are compared. Rows are matched by the key column using identical() for element-wise comparison, so type differences (e.g., integer vs. double) will be flagged as differences.

The values of the key column must be unique in both data frames.

See also

Other data.equal: allDuplicated(), allIdentical()

Examples

x <- data.frame(id = c("A", "B", "C"), v1 = 1:3, v2 = c(10, 20, 30))
y <- data.frame(id = c("A", "B", "D"), v1 = c(1L, 9L, 4L), v2 = c(10, 20, 40))
compareDataFrames(x, y, key = "id")
#> $identical
#> [1] FALSE
#> 
#> $onlyInX
#>   id v1 v2
#> 3  C  3 30
#> 
#> $onlyInY
#>   id v1 v2
#> 3  D  4 40
#> 
#> $diffs
#>   id diffCols
#> 1  B       v1
#>