[R] Getting minimum value of a column according a factor column of a dataframe

[javad bayat]

Dear all;
I am trying to get the minimum value of a column based on a factor column
of the same data frame. My data frame is like the below:
       Code               Y               M                D
 Q
     N              O
41003 81 1 19 0.16 7.17 2.5
41003 77 9 22 0.197 6.8 2.2
41003 79 7 28 0.21 4.7 6.2
41005 79 8 17 0.21 5.5 7.2
41005 80 10 30 0.21 6.84 2.6
41005 80 12 20 0.21 6.84 2.4
41005 79 6 14 0.217 5.61 3.55
41009 79 2 21 0.218 5.56 4.04
41009 79 5 27 0.218 6.4 3.12
41009 80 11 29 0.22 6.84 2.8
41009 78 5 28 0.232 6 3.2
41009 81 8 20 0.233 6.39 1.6
41009 79 9 30 0.24 5.6 7.5
41017 79 10 20 0.24 5.3 7.1
41017 80 7 30 0.24 6.73 2.6

I want to get the minimum value of the "Q" column with the whole row
values, according to the "Code"  column  which is a factor. Overall it will
give me 4 rows, with the value of "Q". Below is a code that I used but it
did not give me what I wanted.

> x[which(x$Q == min(x$Q)),]

Sincerely



-- 
Best Regards
Javad Bayat
M.Sc. Environment Engineering
Alternative Mail: bayat194 using yahoo.com

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