R help - Feb 2010 - simple subtraction in a single vector

OK, this is very elementary, but I need help.  I have looked in Verzani,
past postings etc.

Problem:  I need to subtract the "length" date between "h4"
and "a3"  #which
would be 4-1
I would rather not convert the two columns into four columns (with headings
being "a3","a4","c4","h4").


DF <- data.frame(length=c(1,2,3,4),
Tanks=c("a3","a4","c4","h4"))

???

Much appreciated, keith

	[[alternative HTML version deleted]]

Tena koe Keith

?which

perhaps.  As in:

which(Tanks=='h4')-which(Tanks=='a3')

HTH ...

Peter Alspach
> -----Original Message-----
> From: r-help-bounces at r-project.org 
> [mailto:r-help-bounces at r-project.org] On Behalf Of Marlin Keith Cox
> Sent: Wednesday, 10 February 2010 3:37 p.m.
> To: r-help at r-project.org
> Subject: [R] simple subtraction in a single vector
> 
> OK, this is very elementary, but I need help.  I have looked 
> in Verzani, past postings etc.
> 
> Problem:  I need to subtract the "length" date between
"h4"
> and "a3"  #which would be 4-1 I would rather not convert the 
> two columns into four columns (with headings being 
> "a3","a4","c4","h4").
> 
> 
> DF <- data.frame(length=c(1,2,3,4),
> Tanks=c("a3","a4","c4","h4"))
> 
> ???
> 
> Much appreciated, keith
> 
> 	[[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.
>

Not exactly sure what you are asking: is this it
> DF <- data.frame(length=c(1,2,3,4),
+
Tanks=c("a3","a4","c4","h4"))
> DF
  length Tanks
1      1    a3
2      2    a4
3      3    c4
4      4    h4
> DF$length[DF$Tanks == 'h4'] - DF$length[DF$Tanks == 'a3']
[1] 3
>

On Tue, Feb 9, 2010 at 9:37 PM, Marlin Keith Cox <marlinkcox at gmail.com>
wrote:
> OK, this is very elementary, but I need help. ?I have looked in Verzani,
> past postings etc.
>
> Problem: ?I need to subtract the "length" date between
"h4" and "a3" ?#which
> would be 4-1
> I would rather not convert the two columns into four columns (with headings
> being "a3","a4","c4","h4").
>
>
> DF <- data.frame(length=c(1,2,3,4),
> Tanks=c("a3","a4","c4","h4"))
>
> ???
>
> Much appreciated, keith
>
> ? ? ? ?[[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?