Question

I’m having a difficulty properly shrinking down the row numbers in a data frame.

I have a data set named “mydata” which I imported from a text file using R. The data frame has about 200 rows with 10 columns.

I removed the row number 3, 7, 9, 199 by using:

mydata <- mydata[-c(3, 7, 9, 199),]

When I run this command, the row 3,7,9,199 are gone from the list but the row number doesn’t automatically shrink down to 196, but stays at 200. I feel like somehow these row numbers are attached to each “row” as part of the dataframe?

How do I fix this problem?

What puzzles me even more is that when I import the textfile using R Studio, I don’t have any problem. (I see 196 when I run the above command). But when using R, I can’t change the row number in a dataframe that matches the actual number of rows in the list.

Can anyone please tell me how to fix this??

Answer 1

You can simply do:

rownames(mydata) <- NULL

after performing the subsetting.

For example:

> mydata = data.frame(a=1:10, b=11:20)
> mydata = mydata[-c(6, 8), ]
> mydata
    a  b
1   1 11
2   2 12
3   3 13
4   4 14
5   5 15
7   7 17
9   9 19
10 10 20
> rownames(mydata) <- NULL
> mydata
   a  b
1  1 11
2  2 12
3  3 13
4  4 14
5  5 15
6  7 17
7  9 19
8 10 20