Getting minimum value of a column according a factor column of a dataframe

do.call(rbind,by(df1, df1$Code, \(x)x[which.min(x$Q),]))

Hello,

OK, what about


res <- lapply(split(df1, df1$Code), \(x) x[which.min(x$Q),])
do.call(rbind, res)
#         Code  Y  M  D     Q    N    O
#  41003 41003 81  1 19 0.160 7.17 2.50
#  41005 41005 79  8 17 0.210 5.50 7.20
#  41009 41009 79  2 21 0.218 5.56 4.04
#  41017 41017 79 10 20 0.240 5.30 7.10


A dplyr solution.



suppressPackageStartupMessages(library(dplyr))

df1 %>%
   group_by(Code) %>%
   slice_min(Q) %>%
   slice_head(n = 1)
#  # A tibble: 4 ? 7
#  # Groups:   Code [4]
#    Code      Y     M     D     Q     N     O
#    <fct> <int> <int> <int> <dbl> <dbl> <dbl>
#  1 41003    81     1    19 0.16   7.17  2.5
#  2 41005    79     8    17 0.21   5.5   7.2
#  3 41009    79     2    21 0.218  5.56  4.04
#  4 41017    79    10    20 0.24   5.3   7.1



Hope this helps,

Rui Barradas


?s 05:56 de 25/08/2022, javad bayat escreveu:

Dear all,
Many thanks for your suggested methods and codes, but unfortunately they
did not give the desired results.
All the codes you have provided are correct but they did not represent the
whole row which is related to the minimum of "Q".
The code must result in 4 rows, with the minimum value of "Q" and other
column values, as below:

        Code

               Y

               M

                D

            Q

             N

              O

41003

81

1

19

0.16

7.17

2.5

41005

79

8

17

0.21

5.5

7.2

41009

79

2

21

0.218

5.56

4.04
41017 79 10 20 0.24 5.3 7.1






Sincerely



























































































41017 79 10 20 0.24 5.3 7.1















On Wed, Aug 24, 2022 at 9:24 PM Rui Barradas <ruipbarradas at sapo.pt> wrote:

Hello,

Here are two options, the 1st outputs a vector, the 2nd a data.frame.


x<-'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'
df1 <- read.table(textConnection(x))
names(df1) <- scan(what = character(),
                     text = 'Code Y M D Q N O')
df1$Code <- factor(df1$Code)

# 1st option
with(df1, tapply(Q, Code, min))
#  41003 41005 41009 41017
#  0.160 0.210 0.218 0.240

# 2nd option
aggregate(Q ~ Code, df1, min)
#     Code     Q
#  1 41003 0.160
#  2 41005 0.210
#  3 41009 0.218
#  4 41017 0.240


Hope this helps,

Rui Barradas

?s 08:44 de 24/08/2022, javad bayat escreveu:

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