R help - Jul 2011 - plotting date data over couple of months

Hi .. i am a beginner in R 

I have data in the format of 

date
04/27/11
04/27/11
04/30/11
04/30/11
05/03/11
05/03/11
05/04/11....

Now i want to plot the data something like this on x-axis... 
     
             ------------------
               27 28 29 30 1 2 3 4 
               April             May
I also wanted to know how to place a "*" when a date is missing from
the
data.. 

my other question is plotting the error bars.. since you can see that i have
dates repeating. how to plot the error bars for count number of dates
detected... 

I would appreciate if someone could answer as soon as possible... 

thank you in advance.. 

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On Jul 13, 2011, at 6:56 PM, vamshi999 wrote:
> Hi .. i am a beginner in R
>
> I have data in the format of
>
> date
> 04/27/11
> 04/27/11
> 04/30/11
> 04/30/11
> 05/03/11
> 05/03/11
> 05/04/11....
So they are not yet dates, but rather character vectors. R dates don't  
look like that unless you make special efforts to mess them up.
>
> Now i want to plot the data something like this on x-axis...
>
>             ------------------
>               27 28 29 30 1 2 3 4
>               April             May
> I also wanted to know how to place a "*" when a date is missing
from
> the
> data..
If you convert to dates, then the axis function should be able to  
properly label a plot.
Read:

?DateTimeClasses
>
> my other question is plotting the error bars.. since you can see  
> that i have
> dates repeating. how to plot the error bars for count number of dates
> detected...
Need a better description of the data. So far you have only said you  
have dates. You should probably... no, make that definitely...  read  
the Posting Guide.
>
> I would appreciate if someone could answer as soon as possible...
Answers given to the extent possible given the limitations of the  
question.
>
> thank you in advance..
>
--

David Winsemius, MD
West Hartford, CT

I am sorry i was not clear in my early post.... 

I have used the below code to change my data into date format.. 

r<-as.POSIXlt(paste(data2$date,data2$time))
library(gsubfn)
library(chron)
r<-as.chron(r)

data2$date<-strftime(strptime(r, format="(%m/%d/%y
%H:%M:%S)"),"%Y-%m-%d")
data2$time<-strftime(strptime(r, format="(%m/%d/%y
%H:%M:%S)"),"%H:%M:%S")

now i have a date variable in the below format.. 

"2011-04-20" 

while plotting dates using the above format.. i was getting the x-axis in
this way.. 

        ----------------------
        2011-04-29    2011-05-05

but i want the values in my x-axis to be in this format.. 

                 ------------------ 
               27 28 29 30 1 2 3 4 
               April             May 


about the error plots.... i was not able to compute the mean and sd values
.. 

My data has  the following columns.. 

date, time, height..

 this is the bird data which we recorded.. so i have date, time, height at
which the birds are being detected . so now i want to plot errorbar for
total no.of birds detected on each day.. 

for a simple plot ..i used.. counts<-table(data$date).. i was able to get
the count on each day.. 

then.. barplot(counts).. but i was not able to calculate the mean and sd for
counts.. 

thank you 

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