R help - May 2008 - how to use substring match as condition?

Hi,

How can I use a substring match as a condition in a subset command?

Sth like this:

subset(input, field1=="blah1" & field2=="blah2") # but
now with substring
match in field2

subset(input, field1=="blah1" & field3 *substringmatch*
"blah3")

I've tried with gsub, but it won't work:

subset(input, field1=="blah1" &
gsub("blah3","",input$field3))

	[[alternative HTML version deleted]]

Something like this may be close to what you want:

subset(input, field1=="blah1" &
!is.na(charmatch("blah3",input$field3)))
 
---

-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org]
On Behalf Of Albert Vilella
Sent: 29 May 2008 11:38
To: r-help at r-project.org
Subject: [R] how to use substring match as condition?

Hi,

How can I use a substring match as a condition in a subset command?

Sth like this:

subset(input, field1=="blah1" & field2=="blah2") # but
now with
substring match in field2

subset(input, field1=="blah1" & field3 *substringmatch*
"blah3")

I've tried with gsub, but it won't work:

subset(input, field1=="blah1" &
gsub("blah3","",input$field3))

	[[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.

On Thu, 29 May 2008, Albert Vilella wrote:
> Hi,
>
> How can I use a substring match as a condition in a subset command?
>
Perhaps

 	subset(input, field1=="blah1" &
regexpr("blah2",field3) != -1 )

??

Study in

 	example(gsub)

the regexpr example

and in

 	?gsub

the 'Value' section as it pertains to regexpr.


HTH,

Chuck
> Sth like this:
>
> subset(input, field1=="blah1" & field2=="blah2") #
but now with substring
> match in field2
>
> subset(input, field1=="blah1" & field3 *substringmatch*
"blah3")
>
> I've tried with gsub, but it won't work:
>
> subset(input, field1=="blah1" &
gsub("blah3","",input$field3))
>
> 	[[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.
>
Charles C. Berry                            (858) 534-2098
                                             Dept of Family/Preventive Medicine
E mailto:cberry at tajo.ucsd.edu	            UC San Diego
http://famprevmed.ucsd.edu/faculty/cberry/  La Jolla, San Diego 92093-0901