Count specific data in a data frame & display

Question

am having exam dataframe with student.id marks

student.id  marks
     2         2
     2         2
     2        -1
     3        -1
     3        -1  
     3         2
     4         2
     4        -1
     5         2
     5         2
     5         2

how could i sum total marks for a specific student.id like below table

  student.id     total-marks
       2           
       3
       4
       5

how can i obtain the above table with respective total marks ? thanks

Exactly the same question is asked [HERE](http://stackoverflow.com/questions/1660124/how-to-sum-a-variable-by-group) Please have a look! — 989, May 27 '16 at 11:06

score 0 · Accepted Answer · answered May 27 '16 at 11:14

0

If you data.frame is callesd df, this should work:

 aggregate(marks~student.id,df,FUN="sum")

answered May 27 '16 at 11:14

Otto_K

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Count specific data in a data frame & display

1 Answers1