merge {joyn}

Merge two data frames

Description

This is a joyn wrapper that works in a similar fashion to base::merge and data.table::merge, which is why merge masks the other two.

Usage

merge(
  x,
  y,
  by = NULL,
  by.x = NULL,
  by.y = NULL,
  all = FALSE,
  all.x = all,
  all.y = all,
  sort = TRUE,
  suffixes = c(".x", ".y"),
  no.dups = TRUE,
  allow.cartesian = getOption("datatable.allow.cartesian"),
  match_type = c("m:m", "m:1", "1:m", "1:1"),
  keep_common_vars = TRUE,
  ...
)

Arguments

x, y

data tables. y is coerced to a data.table if it isn't one already.

by

A vector of shared column names in x and y to merge on. This defaults to the shared key columns between the two tables. If y has no key columns, this defaults to the key of x.

by.x, by.y

Vectors of column names in x and y to merge on.

all

logical; all = TRUE is shorthand to save setting both all.x = TRUE and all.y = TRUE.

all.x

logical; if TRUE, rows from x which have no matching row in y are included. These rows will have 'NA's in the 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 above.

sort

logical. If TRUE (default), the rows of the merged data.table are sorted by setting the key to the by / by.x columns. If FALSE, unlike base R's merge for which row order is unspecified, the row order in x is retained (including retaining the position of missings when all.x=TRUE), followed by y rows that don't match x (when all.y=TRUE) retaining the order those appear in y.

suffixes

A character(2) specifying the suffixes to be used for making non-by column names unique. The suffix behaviour works in a similar fashion as the merge.data.frame method does.

no.dups

logical indicating that suffixes are also appended to non-by.y column names in y when they have the same column name as any by.x.

allow.cartesian

See allow.cartesian in [.data.table.

match_type

character: one of "m:m", "m:1", "1:m", "1:1". Default is "1:1" since this the most restrictive. However, following Stata's recommendation, it is better to be explicit and use any of the other three match types (See details in match types sections).

keep_common_vars

logical: If TRUE, it will keep the original variable from y when both tables have common variable names. Thus, the prefix "y." will be added to the original name to distinguish from the resulting variable in the joined table.

...

Arguments passed on to joyn

y_vars_to_keep

character: Vector of variable names in y that will be kept after the merge. If TRUE (the default), it keeps all the brings all the variables in y into x. If FALSE or NULL, it does not bring any variable into x, but a report will be generated.

reportvar

character: Name of reporting variable. Default is ".joyn". This is the same as variable "_merge" in Stata after performing a merge. If FALSE or NULL, the reporting variable will be excluded from the final table, though a summary of the join will be display after concluding.

update_NAs

logical: If TRUE, it will update NA values of all variables in x with actual values of variables in y that have the same name as the ones in x. If FALSE, NA values won't be updated, even if update_values is TRUE

update_values

logical: If TRUE, it will update all values of variables in x with the actual of variables in y with the same name as the ones in x. NAs from y won't be used to update actual values in x. Yet, by default, NAs in x will be updated with values in y. To avoid this, make sure to set update_NAs = FALSE

verbose

logical: if FALSE, it won't display any message (programmer's option). Default is TRUE.

Value

data.table merging x and y

Examples

x1 = data.frame(id = c(1L, 1L, 2L, 3L, NA_integer_),
                t  = c(1L, 2L, 1L, 2L, NA_integer_),
                x  = 11:15)
y1 = data.frame(id = c(1,2, 4),
                y  = c(11L, 15L, 16))
joyn::merge(x1, y1, by = "id")
# example of using by.x and by.y
x2 = data.frame(id1 = c(1, 1, 2, 3, 3),
                id2 = c(1, 1, 2, 3, 4),
                t   = c(1L, 2L, 1L, 2L, NA_integer_),
                x   = c(16, 12, NA, NA, 15))
y2 = data.frame(id  = c(1, 2, 5, 6, 3),
                id2 = c(1, 1, 2, 3, 4),
                y   = c(11L, 15L, 20L, 13L, 10L),
                x   = c(16:20))
jn <- joyn::merge(x2,
            y2,
            match_type = "m:m",
            all.x = TRUE,
            by.x = "id1",
            by.y = "id2")
# example with all = TRUE
jn <- joyn::merge(x2,
            y2,
            match_type = "m:m",
            by.x = "id1",
            by.y = "id2",
            all = TRUE)