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

[javad bayat]

Dear Rui;
Thank you very much. Both of your codes worked correctly. Now I can see the
whole row's value.
But I found a problem in the results. When I run your codes, the results
are shown in a sorted table. I do not know why the results have been sorted
according to the "Code" column, smallest to largest. Is there any way to
get the results like their order in the first data frame (bilan2)? I used
your codes as follow:

> bilan3 <- lapply(split(bilan2, bilan2$Code), \(x) x[which.min(x$Q),])
> bilan3 = data.frame(do.call(rbind, bilan3))
Sincerely



On Thu, Aug 25, 2022 at 11:52 AM Rui Barradas <ruipbarradas using sapo.pt> wrote:

> 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
>
>
> Às 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
> >
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> >
> > Sincerely
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> > 41017 79 10 20 0.24 5.3 7.1
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> > On Wed, Aug 24, 2022 at 9:24 PM Rui Barradas <ruipbarradas using 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$Code)
> >>
> >> # 1st option
> >> with(df1, tapply(Q, Code, min))
> >> #  41003 41005 41009 41017
> >> #  0.160 0.210 0.218 0.240
> >>
> >> # 2nd option
> >> aggregate(Q ~ Code, df1, min)
> >> #     Code     Q
> >> #  1 41003 0.160
> >> #  2 41005 0.210
> >> #  3 41009 0.218
> >> #  4 41017 0.240
> >>
> >>
> >> Hope this helps,
> >>
> >> Rui Barradas
> >>
> >> Às 08:44 de 24/08/2022, javad bayat escreveu:
> >>> Dear all;
> >>> I am trying to get the minimum value of a column based on a factor
> column
> >>> of the same data frame. My data frame is like the below:
> >>>          Code               Y               M                D
> >>>    Q
> >>>        N              O
> >>> 41003 81 1 19 0.16 7.17 2.5
> >>> 41003 77 9 22 0.197 6.8 2.2
> >>> 41003 79 7 28 0.21 4.7 6.2
> >>> 41005 79 8 17 0.21 5.5 7.2
> >>> 41005 80 10 30 0.21 6.84 2.6
> >>> 41005 80 12 20 0.21 6.84 2.4
> >>> 41005 79 6 14 0.217 5.61 3.55
> >>> 41009 79 2 21 0.218 5.56 4.04
> >>> 41009 79 5 27 0.218 6.4 3.12
> >>> 41009 80 11 29 0.22 6.84 2.8
> >>> 41009 78 5 28 0.232 6 3.2
> >>> 41009 81 8 20 0.233 6.39 1.6
> >>> 41009 79 9 30 0.24 5.6 7.5
> >>> 41017 79 10 20 0.24 5.3 7.1
> >>> 41017 80 7 30 0.24 6.73 2.6
> >>>
> >>> I want to get the minimum value of the "Q" column with the whole row
> >>> values, according to the "Code"  column  which is a factor. Overall it
> >> will
> >>> give me 4 rows, with the value of "Q". Below is a code that I used but
> it
> >>> did not give me what I wanted.
> >>>
> >>>> x[which(x$Q == min(x$Q)),]
> >>>
> >>> Sincerely
> >>>
> >>>
> >>>
> >>
> >
> >
>


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

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