[R] by group

[Avi Gross]

Jim,

Your code gives the output in quite a different format and as an object of
class "by" that is not easily convertible to a data.frame. So, yes, it is an
answer that produces the right numbers but not in the places or data
structures I think they (or if it is HW ...) wanted.

Trivial standard cases are often handled by a single step but more complex
ones often suggest a multi-part approach.

Of course Val gets to decide what approach works best for them within
whatever constraints we here are not made aware of. If this is a class
assignment, it likely would be using only tools discussed in the class. So I
would not suggest using a dplyr/tidyverse approach if that is not covered or
even part of a class. If this is a project in the real world, it becomes a
matter of programming taste and convenience and so on.

Maybe Val can share more about the situation so we can see what is helpful
and what is not. Realistically, I can think of way too many ways to get the
required output.

-----Original Message-----
From: R-help <r-help-bounces using r-project.org> On Behalf Of Jim Lemon
Sent: Monday, November 1, 2021 6:25 PM
To: Val <valkremk using gmail.com>; r-help mailing list <r-help using r-project.org>
Subject: Re: [R] by group

Hi Val,
I think you answered your own question:

by(dat$wt,dat[,c("Sex","Year")],mean)

Jim

On Tue, Nov 2, 2021 at 8:09 AM Val <valkremk using gmail.com> wrote:
>
> Hi All,
>
> How can I generate mean by group. The sample data looks like as 
> follow, dat<-read.table(text="Year Sex wt
> 2001 M 15
> 2001 M 14
> 2001 M 16
> 2001 F 12
> 2001 F 11
> 2001 F 13
> 2002 M 14
> 2002 M 18
> 2002 M 17
> 2002 F 11
> 2002 F 15
> 2002 F 14
> 2003 M 18
> 2003 M 13
> 2003 M 14
> 2003 F 15
> 2003 F 10
> 2003 F 11  ",header=TRUE)
>
> The desired  output  is,
>              M        F
> 2001    15        12
> 2002    16.33   13.33
> 2003    15          12
>
> Thank you,
>
> ______________________________________________
> R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see 
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide 
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

______________________________________________
R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.