[R] Subset a data frame with specific date

[Bert Gunter]

That's fine, but do note that the which() function is wholly unnecessary in
your last line as R allows logical indexing. Perhaps another topic you need
to study.

-- Bert



On Mon, Jan 13, 2020 at 10:56 PM ani jaya <gaaauul using gmail.com> wrote:

> Dear Jeff and Bert,
>
> Thank you very much for your correction and explanation.
> And yes, I need to study about date format more.
> Sorry for HTML mail, don't realize.
>
> I was able to subset the data that I want.
>
> mjo30<-read.table("rmm.txt", header=FALSE, skip=4234, nrows=10957)
> mjo30$V8<-NULL
> names(mjo30)<-c("year","month","day", "rmm1","rmm2","phase","amp")
> mjo3<-as.Date(with(mjo30,paste(year,month, day, sep="-")),"%Y-%m-%d")
> mjo<-mjo30[which(mjo3%in%date),]
>
> head(mjo)
>      year month day      rmm1      rmm2 phase      amp
> 115  1986     4  25 -0.319090 -0.363030     2 0.483332
> 526  1987     6  10  1.662870  0.291632     5 1.688250
> 977  1988     9   3 -0.604950 -0.299850     1 0.675181
> 1374 1989    10   5  0.972298 -0.461030     4 1.076060
> 1760 1990    10  26 -1.183110 -1.589810     2 1.981730
> 1953 1991     5   7 -0.317180  0.953061     7 1.004450
>
>
> Best,
> Ani
>
>
> On Tue, Jan 14, 2020 at 3:20 PM Jeff Newmiller <jdnewmil using dcn.davis.ca.us>
> wrote:
> >
> > The dput function is for re-creating an R object in another R workspace,
> so it uses fundamental base types to define objects. A Date is really the
> number of days since a specific date (typically 1970-01-01) that get
> converted to look like dates whenever you display or print them, so what
> you are seiing are those numbers. If we enter the R code returned by dput
> into our R session we will be able to see the dates.
> >
> > Your mjo30 table seems to call the day of the month the "date"... which
> is confusing. I would combine those three columns into one like
> >
> > mjo30$Dt <- as.Date( ISOdate( mjo30$year, mjo30$month, mjo30$date ) )
> >
> > You could then use indexing
> >
> > mjo30[ date[1] == mjo30$Dt, ]
> >
> > or
> >
> > mjo30[ mjo30$Dt %in% date, ]
> >
> > but the subset function would not work in this case because you have two
> different objects (a column in mjo30 and a vector in your global
> environment) both referred to as 'date'.
> >
> > On January 13, 2020 8:53:38 PM PST, ani jaya <gaaauul using gmail.com> wrote:
> > >Good morning R-Help,
> > >
> > >I have a dataframe with 7 columns and 10000+ rows. I want to
> > >subset/extract
> > >those data frame with specific date (not in order). Here the head of my
> > >data frame:
> > >
> > >head(mjo30)  year month date      rmm1     rmm2 phase     amp
> > >1 1986     1    1 -0.326480 -1.55895     2 1.59277
> > >2 1986     1    2 -0.417700 -1.82689     2 1.87403
> > >3 1986     1    3  0.032915 -2.40150     3 2.40172
> > >4 1986     1    4  0.492743 -2.49216     3 2.54041
> > >5 1986     1    5  0.585106 -2.76866     3 2.82981
> > >6 1986     1    6  0.665013 -3.13883     3 3.20851
> > >
> > >and here my specific date:
> > >> date [1] "1986-04-25" "1987-06-10" "1988-09-03" "1989-10-05"
> > >"1990-10-26" "1991-05-07" "1992-11-19" "1993-01-23" "1994-12-04"
> > >[10] "1995-05-11" "1996-10-04" "1997-04-29" "1998-04-08" "1999-01-16"
> > >"2000-08-01" "2001-10-02" "2002-05-08" "2003-04-01"
> > >[19] "2004-05-07" "2005-09-02" "2006-12-30" "2007-09-03" "2008-10-24"
> > >"2009-11-14" "2010-07-05" "2011-04-30" "2012-05-21"
> > >[28] "2013-04-07" "2014-05-07" "2015-07-26"
> > >
> > >And also I was confused when I dput my date, it show like this:
> > >> dput(date)structure(c(5958, 6369, 6820, 7217, 7603, 7796, 8358, 8423,
> > >9103,
> > >9261, 9773, 9980, 10324, 10607, 11170, 11597, 11815, 12143, 12545,
> > >13028, 13512, 13759, 14176, 14562, 14795, 15094, 15481, 15802,
> > >16197, 16642), class = "Date")
> > >
> > >what is that mean? I mean why it is not recall the dates but some
> > >values (5958,6369,7217,..)?
> > >
> > >Any comment and recommendation is appreciate.  Thank you.
> > >
> > >Best,
> > >
> > >Ani
> > >
> > >       [[alternative HTML version deleted]]
> > >
> > >______________________________________________
> > >R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
> > >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.
> >
> > --
> > Sent from my phone. Please excuse my brevity.
>
> ______________________________________________
> R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
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> and provide commented, minimal, self-contained, reproducible code.
>

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