R help - Feb 2013 - x-axis labelling

Hi Folks!

I have a question regarding an issue on which I´ve read a few threads but
can´t resolve --> Labelling every other tick mark on the x-axis using
factors. Here´s an example:

db<-data.frame(date=as.factor(c(1:50)),var=rnorm(50))
barplot(db$var,names.arg=levels(db$date),las=2,cex.axis=0.8,cex=0.8)

This labels all the tickmarks in my barplot, which is the default behavior.
I would like to label every other tick mark in the barplot -->
1,3,5,7 and so on.

Thank you very much for your help!


All the best,

A

-- 
Alfredo Tello (http://alfredotello.com)
Sustainable Aquaculture Group
Institute of Aquaculture
University of Stirling
Scotland, UK.

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On Feb 1, 2013, at 9:30 AM, Alfredo Tello wrote:
> Hi Folks!
>
> I have a question regarding an issue on which I?ve read a few  
> threads but
> can?t resolve --> Labelling every other tick mark on the x-axis using
> factors. Here?s an example:
>
Why not:

db<-data.frame(date=as.factor(c(1:50)),var=rnorm(50))
barplot(db$var,names.arg=ifelse( rep( c(TRUE,FALSE),  
length=length(levels(db$date) ) ),  levels(db$date),  
""),las=2,cex.axis=0.8,cex=0.8)

barplot(db$var,names.arg=ifelse( c(TRUE,FALSE),  levels(db$date),  
""},las=2,cex.axis=0.8,cex=0.8)


-- David.
> This labels all the tickmarks in my barplot, which is the default  
> behavior.
> I would like to label every other tick mark in the barplot -->
> 1,3,5,7 and so on.
>
> Thank you very much for your help!
>
>
> All the best,
>
> A
>
> -- 
> Alfredo Tello (http://alfredotello.com)
> Sustainable Aquaculture Group
> Institute of Aquaculture
> University of Stirling
> Scotland, UK.
>
> 	[[alternative HTML version deleted]]
>
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Alameda, CA, USA