Re: [R] Subsetting data by date

From: Williams, Robin <robin.williams_at_metoffice.gov.uk>
Date: Mon, 21 Jul 2008 15:37:40 +0100

Thanks very much for this. The dates are in fact in 3-character form (i.e. sep and not sept).
  Any suggestions as to where one can start to learn the R language? Up until now, I have only entered simple commands in the terminal.

Best wishes,
Robin Williams
Met Office summer intern - Health Forecasting robin.williams_at_metoffice.gov.uk
-----Original Message-----
From: Gabor Grothendieck [mailto:ggrothendieck_at_gmail.com] Sent: Monday, July 21, 2008 3:26 PM
To: Williams, Robin
Cc: R-help_at_r-project.org
Subject: Re: [R] Subsetting data by date

Continuing on, to just get points from May to Sep

mo <- as.numeric(format(time(z), "%m"))
z.summer <- z[mo >= 5 & mo <= 9]

If in your case z is multivariate rather than univariate (as it is in our example) then it would be:
z.summer <- z[mo >= 5 & mo <= 9, ]

On Mon, Jul 21, 2008 at 9:55 AM, Gabor Grothendieck <ggrothendieck_at_gmail.com> wrote:
> Try this:
>
> Lines <- "Date,Temp
> 1-Apr-1997,50
> 3-Sept-2001,60"
>
> library(zoo)
>
> # function to reduce 4 char mos to 3 char convert.date <- function(x,
> format) as.Date(sub("(-...).-", "\\1-", x), format)
>
> # z <- read.zoo("myfile.csv", header = TRUE, sep = ",", FUN =
> convert.date, format = "%d-%b-%Y") z <-
> read.zoo(textConnection(Lines), header = TRUE, sep = ",", FUN =
> convert.date, format = "%d-%b-%Y")
>
> plot(z)
>
> If the dates are actually three letters, i.e. Sep and not Sept, then
> you could eliminate convert.date and simplify the read.zoo line to:
>
> z <- read.zoo(textConnection(Lines), header = TRUE, sep = ",", format
> = "%d-%b-%Y")
>
> See the zoo package documentation and its three vignettes as well as
> ?read.zoo ?strptime and ?plot.zoo and also look at the dates article
in R News 4/1.
>
>
> On Mon, Jul 21, 2008 at 9:31 AM, Williams, Robin
> <robin.williams_at_metoffice.gov.uk> wrote:
>> Hi all,
>> Firstly I appologise if this question has been answered previously,
>> however searching of the archives and the internet generally has not
>> yielded any results.
>>
>> I am looking in to the effects of summer weather conditions
>> (temperature, humidity etc), on the incidences of a breathing
>> disorder brought on through smoking (COPD). I am fairly new to R and
>> completely new to the idea of writing R scripts, subsetting
>> dataframes etc. I am working on a 12 week summer placement at the Met

>> Office, UK, having just finished my second year of a mathematics
course at university.
>>
>> Basically I have data between January 1 1997 and December 31 2007.
>> However as I am only interest in the summer months (which I have
>> defined to be between May 1 and September 30), I would like to
>> extract the relevant data in R in a timely manner. Obviously I could
>> go and open my csv files in excel, cut and paste the relevant data,
>> etc, however I would like to maximise R's potential as I feel it will

>> stand me in better stead in the long run.
>> Currently the dates are in the form
>> 1-Apr-1997,
>> 3-Sept-2001,
>> etc.
>> I will create a data.frame with date as one of the variables, the
>> others being (initially) temperature, humidity, and Admissions (the
>> number of hospital admissions for COPD exaserbations).
>> Please could somebody tell me if there is a simple way to extract
>> the data I want, and if so perhaps a sample command to get me going?
>> Do I first need to format the dates to some numeric-only format? As I

>> say, I could use Excel to create the files in the right format, but I

>> will be dealing with a lot more variables in the future (perhaps up
>> to 8) and so this will become a pain-staking process.
>>
>> Please reply either on or off list.
>>
>> Many thanks for any help.
>> Robin Williams
>> Met Office summer intern - Health Forecasting
>> robin.williams_at_metoffice.gov.uk
>>
>>
>> [[alternative HTML version deleted]]
>>
>> ______________________________________________
>> R-help_at_r-project.org mailing list
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>> PLEASE do read the posting guide
>> http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>>
>



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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. Received on Mon 21 Jul 2008 - 14:45:16 GMT

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