R help - Jul 2011 - matplot with dates/times on horizontal axis

>matplot(timestamp,xymatrix,type='l')
where timestamp is a vector filled with POSIXct objects and xymatrix is 
a numeric 2x2 matrix plots but the horizontal axis labels are raw 
unformatted timestamps.

I would like to format these in any of the available codes for strftime, 
for instance format="%H:%M".

Passing a vector of formatted strings does not work. Any obvious other 
ways fail upon me as well.

Any ideas to make this work?

Thanks in advance,
Alex van der Spek

On 07/12/2011 10:48 PM, Alex van der Spek wrote:
>  >matplot(timestamp,xymatrix,type='l')
>
> where timestamp is a vector filled with POSIXct objects and xymatrix is
> a numeric 2x2 matrix plots but the horizontal axis labels are raw
> unformatted timestamps.
>
> I would like to format these in any of the available codes for strftime,
> for instance format="%H:%M".
>
> Passing a vector of formatted strings does not work. Any obvious other
> ways fail upon me as well.
>
> Any ideas to make this work?
Hi Alex,
I would use the "xaxt" argument to matplot and then add the axis:

matplot(...,xaxt="n")
timelabels<-format(timestamp,"%H:%M")
axis(1,at=timestamp,labels=timelabels)

Jim