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.