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

Thu Aug 25 13:22:25 CEST 2022

The data are sorted by the variable(s) in the group_by() statement. If the variable in the group_by() statement is not correct then you can change it to whatever the correct variable may be. If the calculations are correct, but you want a different sort order then arrange() (from dplyr) would work as would order() and sort() commands. There are many help pages on the web for sorting vectors and dataframes.

Tim

-----Original Message-----
From: R-help <r-help-bounces using r-project.org> On Behalf Of javad bayat
Sent: Thursday, August 25, 2022 3:53 AM
To: Rui Barradas <ruipbarradas using sapo.pt>
Cc: R-help using r-project.org
Subject: Re: [R] Getting minimum value of a column according a factor column of a dataframe

[External Email]

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
> >
> >
> >
> >
> >
> >
> > Sincerely
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> > 41017 79 10 20 0.24 5.3 7.1
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> > 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

        [[alternative HTML version deleted]]

______________________________________________
R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fstat.ethz.ch%2Fmailman%2Flistinfo%2Fr-help&data=05%7C01%7Ctebert%40ufl.edu%7C50403ccd882345d00db908da8689bacb%7C0d4da0f84a314d76ace60a62331e1b84%7C0%7C0%7C637970223349266197%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=OrqS9I1qav2ztgWpW6BtMkFU9wa0s8dMrVAEP834%2FaU%3D&reserved=0
PLEASE do read the posting guide https://nam10.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.r-project.org%2Fposting-guide.html&data=05%7C01%7Ctebert%40ufl.edu%7C50403ccd882345d00db908da8689bacb%7C0d4da0f84a314d76ace60a62331e1b84%7C0%7C0%7C637970223349266197%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=EzG74%2BCS%2FF2ghpT9FKy%2BDm2Qf%2FAARRCJSXxmYBoqoIQ%3D&reserved=0
and provide commented, minimal, self-contained, reproducible code.