1. Join Two Data Frames In R
  2. Concatenate Two Data Frames R
  3. Pandas Dataframe Reindex
  • On: Column or index level names to join on. Must be found in both the left and right DataFrame and/or Series objects. If not passed and leftindex and rightindex are False, the intersection of the columns in the DataFrames and/or Series will be inferred to be the join keys.
  • Concatenate two columns of dataframe in R. Concatenate numeric and string column in R. Concatenate two columns by removing leading and trailing space. Concatenate two or more columns using hyphen(“-”) & space; merge or concatenate two or more columns in R using strc and unite function. Let’s first create the dataframe.
  • Right Join: Returns all records in right dataframe and only matching records from the other; Cross join: Returns all the possible combination of records in both the dataframes; To merge 2 dataframes in R, we use merge function to do so. In this recipe, we will learn how to merge two dataframe in R.
  • Inner join: merge (df1, df2) will work for these examples because R automatically joins the frames by common variable names, but you would most likely want to specify merge (df1, df2, by = 'CustomerId') to make sure that you were matching on only the fields you desired.

Two R data frames can be combined with respect to columns or rows. We will look into both of these ways. To combine data frames based on a common column(s), i.e., adding columns of second data frame to the first data frame with respect to a common column(s), you can use merge function. To combine data frames: with rows of second data frame added to those of the first one, you can use rbind function.

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:

Join Two Data Frames In R

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

before joining them with rbind( ).

Going Further

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

Combine Data Frames in R

In this tutorial, we will learn how to merge or combine two data frames in R programming.

Two R data frames can be combined with respect to columns or rows. We will look into both of these ways.

  • To combine data frames based on a common column(s), i.e., adding columns of second data frame to the first data frame with respect to a common column(s), you can use merge() function.
  • To combine data frames: with rows of second data frame added to those of the first one, you can use rbind() function.

R Combine Data Frames – Merge based on a common column(s)

merge() function is used to merge data frames. The syntax of merge() function is:

where

  • x, y are data frames, or objects to be coerced or combined to one
  • by, by.x, by.y are specifcations of the common columns.
  • sort logical (TRUE or FALSE). Results are sorted on the by columns if TRUE and not if FALSE.

Example 1 – Combine Data Frames in R using merge()

In this example, we take two data frames. The first data frame contains id and name of students. The second data frame contains id and marks of students.

You can combine these two data frames with respect to the common column id using merge() function.

The second data frame is added to the first data frame based on a column. The result is a new data frame with new columns.

This is useful when you collect the experimental data from different sources pertaining to the same experiments. Data from a source contains data collected for certain features while other source collects data for other features. Now, using merge(), you can combine these data to get a single data frame containing all the features values of experiments.

R Combine Data Frames – Concatenate Rows of Data Frame to another Data Frame

rbind() function is used to concatenate data frames. The syntax of rbind() function is:

Join

where

  • x an R6Frame
  • ... additional parameters sent to rbind

Example 2 – Combine Data Frames in R using rbind()

In this example, we take two data frames. The first data frame contains id and name of students. The second data frame also contains id and name of students. Consider that these are two batches of students and we would like to concatenate these.

You can combine these two data frames with respect to rows using rbind() function.

The rows of second data frame are added to that of first data frame. The result is a new data frame with increased number of rows.

Concatenate Two Data Frames R

Conclusion

Pandas Dataframe Reindex

In this R Tutorial, we have learned how to combine R Data Frames based on rows or columns.

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