Merge R Studio

Merge R StudioMerge R Studio

In this tutorial, we will learn 'How to use dplyr Function to Merge Dataframes with multiple keys' in R programming.Advantages to dplyr over base R merge fun. A new data.table based on the merged data tables, and sorted by the columns set (or inferred for) the by argument if argument sort is set to TRUE. Merge is a generic function in base R. It dispatches to either the merge.data.frame method or merge.data.table method depending on the class of its first argument. Note that, unlike SQL, NA is matched against NA (and NaN against NaN.

Adding Columns

To merge two data frames (datasets) horizontally, use the merge function. In most cases, you join two data frames by one or more common key variables (i.e., an inner join).

# merge two data frames by ID
total <- merge(data frameA,data frameB,by='ID')

# merge two data frames by ID and Country
total <- merge(data frameA,data frameB,by=c('ID','Country'))

Adding Rows

To join two data frames (datasets) vertically, use the rbind function. The two data frames must have the same variables, but they do not have to be in the same order.

total <- rbind(data frameA, data frameB)

If data frameA has variables that data frameB does not, then either:

  1. Delete the extra variables in data frameA or
  2. Create the additional variables in data frameB and set them to NA (missing)
Merge r studio

before joining them with rbind( ).

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Going Further

To practice manipulating data frames with the dplyr package, try this interactive course on data frame manipulation in R.

merge is a generic function in base R. It dispatches to either themerge.data.frame method or merge.data.table method depending onthe class of its first argument. Note that, unlike SQL, NA ismatched against NA (and NaN against NaN) while merging.

In versions <= v1.9.4, if the specified columns in by were not thekey (or head of the key) of x or y, then a copy isfirst re-keyed prior to performing the merge. This was less performant as well as memoryinefficient. The concept of secondary keys (implemented in v1.9.4) wasused to overcome this limitation from v1.9.6+. No deep copies are madeany more, thereby improving performance and memory efficiency. Also, there is bettercontrol for providing the columns to merge on with the help of the newly implementedby.x and by.y arguments.

Merge By R Studio

For a more data.table-centric way of merging two data.tables, see[.data.table; e.g., x[y, …]. See FAQ 1.11 for a detailedcomparison of merge and x[y, …].

R Studio Merge Data Frames

If any column names provided to by.x also occur in names(y) but not in by.y,then this data.table method will add the suffixes to those column names. As ofR v3.4.3, the data.frame method will not (leading to duplicate column names in the result) but a patch hasbeen proposed (see r-devel thread here)which is looking likely to be accepted for a future version of R.