R Programming Server Side Programming Programming Mostly, we merge the data frames by columns because column names are considered prominent in data sets but it is also possible to merge two data frames by using rows. Merging by rows is likely to result in more uncleaned data as compared to the merging by columns. To merge both the data frames we will run the below R script. Here I have used the natural join to know more about other types of R data frame joins you can follow the above article link. We use comma (,) to pass both column name as key for merging the data frames.
merge is a generic function whose principal method is for data frames: the default method coerces its arguments to data frames and calls the 'data.frame' method.
By default the data frames are merged on the columns with names they both have, but separate specifications of the columns can be given by by.x and by.y. The rows in the two data frames that match on the specified columns are extracted, and joined together. If there is more than one match, all possible matches contribute one row each. For the precise meaning of ‘match', see match.
Columns to merge on can be specified by name, number or by a logical vector: the name 'row.names' or the number 0 specifies the row names. If specified by name it must correspond uniquely to a named column in the input.
If by or both by.x and by.y are of length 0 (a length zero vector or NULL), the result, r, is the Cartesian product of x and y, i.e., dim(r) = c(nrow(x)*nrow(y), ncol(x) + ncol(y)).
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If all.x is true, all the non matching cases of x are appended to the result as well, with NA filled in the corresponding columns of y; analogously for all.y.
If the columns in the data frames not used in merging have any common names, these have suffixes ('.x' and '.y' by default) appended to try to make the names of the result unique. If this is not possible, an error is thrown.
If a by.x column name matches one of y, and if no.dups is true (as by default), the y version gets suffixed as well, avoiding duplicate column names in the result.
The complexity of the algorithm used is proportional to the length of the answer.
In SQL database terminology, the default value of all = FALSE gives a natural join, a special case of an inner join. Specifying all.x = TRUE gives a left (outer) join, all.y = TRUE a right (outer) join, and both (all = TRUE) a (full) outer join. DBMSes do not match NULL records, equivalent to incomparables = NA in R.
Description
Abbreviation: mrg
A horizontal merge combines data frames horizontally, that is, adds variables (columns) to an existing data frame according to a common shared ID field. Performs the horizontal merge based directly on the standard R merge function. The vertical merge is based on the rbind function in which the two data frames have the same variables but different cases (observations), so the rows build vertically, stacked on top of each other.
The advantages of this lessR function is that it provides a single function for merging data frames, adds text output to the standard R functions that provide feedback regarding properties of the merge, provides more detailed and presumably more useful error messages, and preserves any variable labels that might exist in one or both of the merged data frames.
Usage
Arguments
The name of the first data frame from which to create the merged data frame.
The name of the second data frame from which to create the merged data frame.
Merge Data Frames In R By Row Names
If specified, then signals a horizontal merge and the ID field by which the data frames are merged. Specify 'row_names' for merging according to the row names.
If set to TRUE, no text output. Can change system default with style function.
Additional arguments available in the base R merge function such as all.x=TRUE for retaining all rows of the first data frame even if not matched by a row in the second data table.
Value
The merged data frame is returned, usually assigned the name of d as in the examples below. This is the default name for the data frame input into the lessR data analysis functions.
Details
How To Merge Dataframe In R
Merge creates a merged data frame from two input data frames.
Merge Function In R
If by is specified the merge is horizontal. That is the variables in the second input data frame are presumed different from the variables in the first input data frame. The merged data frame is the combination of variables from both input data frames, with the rows aligned by the value of by, an ID field common to both data frames.
If by is not provided, then the merge is vertical. The variables are presumed the same in each input data frame. The merged data frame consists of the rows of both input data frames. The rows of the first data frame are stacked upon the rows of the second data frame.
The complexity of the algorithm used is proportional to the length of the answer.
In SQL database terminology, the default value of all = FALSE gives a natural join, a special case of an inner join. Specifying all.x = TRUE gives a left (outer) join, all.y = TRUE a right (outer) join, and both (all = TRUE) a (full) outer join. DBMSes do not match NULL records, equivalent to incomparables = NA in R.
Description
Abbreviation: mrg
A horizontal merge combines data frames horizontally, that is, adds variables (columns) to an existing data frame according to a common shared ID field. Performs the horizontal merge based directly on the standard R merge function. The vertical merge is based on the rbind function in which the two data frames have the same variables but different cases (observations), so the rows build vertically, stacked on top of each other.
The advantages of this lessR function is that it provides a single function for merging data frames, adds text output to the standard R functions that provide feedback regarding properties of the merge, provides more detailed and presumably more useful error messages, and preserves any variable labels that might exist in one or both of the merged data frames.
Usage
Arguments
The name of the first data frame from which to create the merged data frame.
The name of the second data frame from which to create the merged data frame.
Merge Data Frames In R By Row Names
If specified, then signals a horizontal merge and the ID field by which the data frames are merged. Specify 'row_names' for merging according to the row names.
If set to TRUE, no text output. Can change system default with style function.
Additional arguments available in the base R merge function such as all.x=TRUE for retaining all rows of the first data frame even if not matched by a row in the second data table.
Value
The merged data frame is returned, usually assigned the name of d as in the examples below. This is the default name for the data frame input into the lessR data analysis functions.
Details
How To Merge Dataframe In R
Merge creates a merged data frame from two input data frames.
Merge Function In R
If by is specified the merge is horizontal. That is the variables in the second input data frame are presumed different from the variables in the first input data frame. The merged data frame is the combination of variables from both input data frames, with the rows aligned by the value of by, an ID field common to both data frames.
If by is not provided, then the merge is vertical. The variables are presumed the same in each input data frame. The merged data frame consists of the rows of both input data frames. The rows of the first data frame are stacked upon the rows of the second data frame.
Guidance and feedback regarding the merge are provided by default. The first five lines of each of the input data frames are listed before the merge operation, followed by the first five lines of the output data frame.
See Also
merge, rbind.
Examples
