Source: R/bind.r

This is an efficient implementation of the common pattern ofdo.call(rbind, dfs) or do.call(cbind, dfs) for binding manydata frames into one.

R: merge multiple data tables. GitHub Gist: instantly share code, notes, and snippets. You may want to combine data from different sources in your analysis. Generally speaking, you can use R to combine different sets of data in three ways: By adding columns: If the two sets of data have an equal set of rows, and the order of the rows is identical, then adding columns makes sense.

Arguments

...

Data frames to combine.

Each argument can either be a data frame, a list that could be a dataframe, or a list of data frames.

When row-binding, columns are matched by name, and any missingcolumns will be filled with NA.

When column-binding, rows are matched by position, so all dataframes must have the same number of rows. To match by value, notposition, see mutate-joins.

.id

Data frame identifier.

When .id is supplied, a new column of identifiers iscreated to link each row to its original data frame. The labelsare taken from the named arguments to bind_rows(). When alist of data frames is supplied, the labels are taken from thenames of the list. If no names are found a numeric sequence isused instead.

.name_repair

One of 'unique', 'universal', or'check_unique'. See vctrs::vec_as_names() for the meaning of theseoptions.

Value

bind_rows() and bind_cols() return the same type asthe first input, either a data frame, tbl_df, or grouped_df.

Details

The output of bind_rows() will contain a column if that columnappears in any of the inputs.

Examples

merge {data.table}R Documentation

Merge two data.tables

Merge Two Tables R

Description

Fast merge of two data.tables.

This merge method for data.table behaves very similarly to that of data.frames with one major exception: By default, the columns used to merge the data.tables are the shared key columns rather than the shared columns with the same names. Set the by, or by.x, by.y arguments explicitly to override this default.

Merge Data Tables R Us

Merge multiple data.tables rMerge function in r

Usage

Arguments

x, y

data tables. y is coerced to a data.table ifit 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 andall.y = TRUE.

all.x

logical; if TRUE, then extra rows will be added to theoutput, one for each row in x that has no matching row iny. These rows will have 'NA's in those columns that areusually filled with values from y. The default is FALSE,so that only rows with data from both x and y areincluded in the output.

all.y

logical; analogous to all.x above.

sort

logical. If TRUE (default), the merged data.table is sorted by setting the key to the by / by.x columns. If FALSE, the result is not sorted.

suffixes

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

allow.cartesian

See allow.cartesian in [.data.table.

...

Not used at this time.

Merge data tables rules

Details

R merge multiple data tables

merge is a generic function in base R. It dispatches to either themerge.data.frame method or merge.data.table method depending on the class of its first argument.

Unlike SQL, NA is matched against NA (and NaN against NaN) while merging.

In versions < v1.9.6, if the specified columns in by was not the key (or head of the key) of x or y, then a copy is first rekeyed prior to performing the merge. This was less performant and memory inefficient.

Merge Table In R

In version v1.9.4 secondary keys was implemented. In v1.9.6, the concept of secondary keys has been extended to merge. No deep copies are made anymore and therefore very performant and memory efficient. Also there is better control for providing the columns to merge on with the help of newly implemented by.x and by.y arguments.

For a more data.table-centric way of merging two data.tables, see [.data.table; e.g., x[y, ...]. See FAQ 1.12 for a detailed comparison of merge and x[y, ...].

Merges on numeric columns: Columns of numeric types (i.e., double) have their last two bytes rounded off while computing order, by defalult, to avoid any unexpected behaviour due to limitations in representing floating point numbers precisely. For large numbers (integers > 2^31), we recommend using bit64::integer64. Have a look at setNumericRounding to learn more.

Value

A new data.table based on the merged data tables, sorted by the columns set (or inferred for) the by argument.

See Also

Data

data.table, as.data.table, [.data.table, merge.data.frame

Examples

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