Reset Sequence or Row Numbers in R Data Frame

In this tutorial, we will learn how to reorder or correct the order of row numbers when a Dataframe is filtered or a subset of a dataframe is accessed.

To reorder the row numbers of a filtered or subset Dataframe, assign row numbers of the dataframe with a sequence of numbers until the length of the filtered dataframe.

Example 1 – Reset Row Numbers in R Data Frame

Consider a Dataframe DF1 shown below.

> DF1 = data.frame(x = c(9, NA, 7, 4), y = c(4, NA, NA, 21))
> DF1
   x  y
1  9  4
3  7 NA
4  4 21

In this original dataframe, the row numbers are ordered from 1 to 4.

Let us filter the rows of this dataframe that do not contain any NAs.

> resultDF = DF1[complete.cases(DF1), ]
> resultDF
  x  y
1 9  4
4 4 21

The second and third rows are trashed out and only rows numbered one and four got into the filtered output dataframe. But the row numbers are not in a sequence.

We need the rows of resultDF to be numbered in sequence without missing any numbers. We will set the rownames with a sequence of numbers with a length equal to number of rows in the dataframe.

> rownames(resultDF) = seq(length=nrow(resultDF))
> resultDF
  x  y
1 9  4
2 4 21

Viola! The numbers are sequenced.



In this R Tutorial, we have learned how to reset the sequence of row numbers of a dataframe obtained through filtering or subsetting.