Filter two variables at same time in R to create a new dataframe

Asked Nov 15 '16 at 13:05

Active Nov 15 '16 at 13:05

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I have a dataframe that is something like this:

STUDENT_ID    SUBJECT_ID     MARK
    1             1           10
    2             1           8
    1             2           9 
    3             2           10 
    4             5           10
    4             3           7 
    3             1           10 
    2             2           9

What I wanted to do is study the correlation between the marks of two subjects, suppose the ones with the ID 1 and 2. Problem is not all students have studied both subjects. So I wanted to create a different table with something like.

STUDENT_ID    SUBJECT 1 MARK    SUBJECT 2 MARK
    1                10                9
    2                 8                9
    3                10               10

Any idea of how could I accomplish that?

asked Nov 15 '16 at 13:05

Sávio Muniz

You can try `library(tidyr);spread(df1, SUBJECT_ID, MARK)` – akrun Nov 15 '16 at 13:07
Or `library(data.table);df1<-data.table(df1);dcast(df1[SUBJECT_ID %in% c(1,2)], STUDENT_ID ~ SUBJECT_ID, value.var = "MARK")` – statespace Nov 15 '16 at 13:11

Filter two variables at same time in R to create a new dataframe

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