I have a data frame with several rows. I want to select some rows with specific rownames (such as stu2,stu3,stu5,stu9) from this dataframe. The input example dataframe is as follows:

 attr1 attr2 attr3 attr4 stu1 0 0 1 0 stu2 -1 1 -1 1 stu3 1 -1 0 -1 stu4 1 -1 1 -1 stu5 -1 1 0 1 stu6 1 -1 1 0 stu7 -1 -1 -1 1 stu8 1 -1 0 -1 stu9 -1 -1 1 -1 stu10 -1 1 0 1

Expected output:

 attr1 attr2 attr3 attr4 stu2 -1 1 -1 1 stu3 1 -1 0 -1 stu5 -1 1 0 1 stu9 -1 -1 1 -1
1

3 Answers

Assuming that you have a data frame called students, you can select individual rows or columns using the bracket syntax, like this:

  • students[1,2] would select row 1 and column 2, the result here would be a single cell.
  • students[1,] would select all of row 1, students[,2] would select all of column 2.

If you'd like to select multiple rows or columns, use a list of values, like this:

  • students[c(1,3,4),] would select rows 1, 3 and 4,
  • students[c("stu1", "stu2"),] would select rows named stu1 and stu2.

Hope I could help.

1

You can also use this:

DF[paste0("stu",c(2,3,5,9)), ] 
df <- data.frame(x=rnorm(10), y=rnorm(10)) rownames(df) <- letters[1:10] df[c('a','b'),]