thr3ads.net - R help - [R] Help with getting ?match to not sort [Nov 2010]

If this information is useful, please help other people find it:
Share via:

Tal Galili

2010-Nov-08 21:09 UTC

[R] Help with getting ?match to not sort

Hello all,

I think I am missing something about the sorting parameter in the
"match"
command/
Here is an example:


a1 <- data.frame(name = c("D", "B", "C",
"A", "A", "C"))
a2 <- data.frame(name = c("A", "B", "C",
"D"), num = 1:4)
a1
a2
merge(a1, a2, sort = F, by.x = T)



The result is:

  name num
1    D   4
2    B   2
3    C   3
4    C   3
5    A   1
6    A   1


While I wish my rows to be in the same order as in a1, they are having some
other order.

What am I missing here?


Thanks.


----------------Contact
Details:-------------------------------------------------------
Contact me: Tal.Galili@gmail.com |  972-52-7275845
Read me: www.talgalili.com (Hebrew) | www.biostatistics.co.il (Hebrew) |
www.r-statistics.com (English)
----------------------------------------------------------------------------------------------

	[[alternative HTML version deleted]]

jim holtman

2010-Nov-08 21:39 UTC

head link

[R] Help with getting ?match to not sort

Missing: a closer reading of the help page --

Value
A data frame. The rows are by default lexicographically sorted on the
common columns, but for sort = FALSE are in an unspecified order.

So sort = FALSE says unspecified.  If you want the original order,
then add a column to the dataframe with the order and then sort the
result.

On Mon, Nov 8, 2010 at 4:09 PM, Tal Galili <tal.galili at gmail.com>
wrote:> Hello all,
>
> I think I am missing something about the sorting parameter in the
"match"
> command/
> Here is an example:
>
>
> a1 <- data.frame(name = c("D", "B", "C",
"A", "A", "C"))
> a2 <- data.frame(name = c("A", "B", "C",
"D"), num = 1:4)
> a1
> a2
> merge(a1, a2, sort = F, by.x = T)
>
>
>
> The result is:
>
> ?name num
> 1 ? ?D ? 4
> 2 ? ?B ? 2
> 3 ? ?C ? 3
> 4 ? ?C ? 3
> 5 ? ?A ? 1
> 6 ? ?A ? 1
>
>
> While I wish my rows to be in the same order as in a1, they are having some
> other order.
>
> What am I missing here?
>
>
> Thanks.
>
>
> ----------------Contact
> Details:-------------------------------------------------------
> Contact me: Tal.Galili at gmail.com | ?972-52-7275845
> Read me: www.talgalili.com (Hebrew) | www.biostatistics.co.il (Hebrew) |
> www.r-statistics.com (English)
>
----------------------------------------------------------------------------------------------
>
> ? ? ? ?[[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list
> 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.
>


-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem that you are trying to solve?

Peter Alspach

2010-Nov-08 21:51 UTC

head link

[R] Help with getting ?match to not sort

Tena koe Tal

sort: logical.  Should the results be sorted on the 'by' columns?

Thus it is clear what sort=TRUE does, sort=FALSE does not do this.  That
doesn't mean it leaves the result in the same order as x (your a1), although
many people (including me at first) assume it does.  It is easy enough to write
a wrapper function to retain the order of x in cases like yours.  For example:

mergeRO <- function (x, y, ...) 
{
    myMerge <- merge(cbind(x, myOrder = 1:nrow(x)), y, ...)
    attr(myMerge, "creation time") <- Sys.time()
    myMerge[order(myMerge$myOrder), colnames(myMerge) != "myOrder"]
}

but I'm not sure this will work in all circumstances in which people might
use merge().

HTH ...

Peter Alspach
> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> project.org] On Behalf Of Tal Galili
> Sent: Tuesday, 9 November 2010 10:10 a.m.
> To: r-help at r-project.org
> Subject: [R] Help with getting ?match to not sort
> 
> Hello all,
> 
> I think I am missing something about the sorting parameter in the
> "match"
> command/
> Here is an example:
> 
> 
> a1 <- data.frame(name = c("D", "B", "C",
"A", "A", "C"))
> a2 <- data.frame(name = c("A", "B", "C",
"D"), num = 1:4)
> a1
> a2
> merge(a1, a2, sort = F, by.x = T)
> 
> 
> 
> The result is:
> 
>   name num
> 1    D   4
> 2    B   2
> 3    C   3
> 4    C   3
> 5    A   1
> 6    A   1
> 
> 
> While I wish my rows to be in the same order as in a1, they are having
> some
> other order.
> 
> What am I missing here?
> 
> 
> Thanks.
> 
> 
> ----------------Contact
> Details:-------------------------------------------------------
> Contact me: Tal.Galili at gmail.com |  972-52-7275845
> Read me: www.talgalili.com (Hebrew) | www.biostatistics.co.il (Hebrew)
> |
> www.r-statistics.com (English)
> -----------------------------------------------------------------------
> -----------------------
> 
> 	[[alternative HTML version deleted]]
> 
> ______________________________________________
> R-help at r-project.org mailing list
> 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.
The contents of this e-mail are confidential and may be subject to legal
privilege.
 If you are not the intended recipient you must not use, disseminate, distribute
or
 reproduce all or any part of this e-mail or attachments.  If you have received
this
 e-mail in error, please notify the sender and delete all material pertaining to
this
 e-mail.  Any opinion or views expressed in this e-mail are those of the
individual
 sender and may not represent those of The New Zealand Institute for Plant and
 Food Research Limited.

Phil Spector

2010-Nov-08 22:13 UTC

head link

[R] Help with getting ?match to not sort

Ted -
    If you want to retain the exact order of the rows of one
of the merged matrices, I think you have to merge them 
"by hand":
> cbind(a1,num=a2[match(a1$name,a2$name),'num'])   name num
1    D   4
2    B   2
3    C   3
4    A   1
5    A   1
6    C   3

 					- Phil Spector
 					 Statistical Computing Facility
 					 Department of Statistics
 					 UC Berkeley
 					 spector at stat.berkeley.edu


On Mon, 8 Nov 2010, Tal Galili wrote:
> Hello all,
>
> I think I am missing something about the sorting parameter in the
"match"
> command/
> Here is an example:
>
>
> a1 <- data.frame(name = c("D", "B", "C",
"A", "A", "C"))
> a2 <- data.frame(name = c("A", "B", "C",
"D"), num = 1:4)
> a1
> a2
> merge(a1, a2, sort = F, by.x = T)
>
>
>
> The result is:
>
>  name num
> 1    D   4
> 2    B   2
> 3    C   3
> 4    C   3
> 5    A   1
> 6    A   1
>
>
> While I wish my rows to be in the same order as in a1, they are having some
> other order.
>
> What am I missing here?
>
>
> Thanks.
>
>
> ----------------Contact
> Details:-------------------------------------------------------
> Contact me: Tal.Galili at gmail.com |  972-52-7275845
> Read me: www.talgalili.com (Hebrew) | www.biostatistics.co.il (Hebrew) |
> www.r-statistics.com (English)
>
----------------------------------------------------------------------------------------------
>
> 	[[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list
> 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.
>

Maybe Matching Threads

Search for more reasonably related threads

R help - Nov 2010 - Help with getting ?match to not sort

[R] Help with getting ?match to not sort

[R] Help with getting ?match to not sort

[R] Help with getting ?match to not sort

[R] Help with getting ?match to not sort

Maybe Matching Threads