[R] filter() question

[Eric Berger]

Hi Eberhard,
Here is one possibility using dplyr.

library(dplyr)
set.seed(3)

## set up some fake data
dtV <- as.Date("2020-08-01") + 0:4
x <- sample(dtV,20,repl=TRUE)
provider <- sample(LETTERS[1:3],20,repl=TRUE)
lDf <- data.frame(Provider=provider,CollectionDate=x,stringsAsFactors=FALSE)

## get min/max date for each provider
a <- lDf %>% dplyr::group_by( Provider ) %>%
  dplyr::mutate( minDt=min(CollectionDate), maxDt=max(CollectionDate)) %>%
  dplyr::summarize( u = min(minDt), v = max(maxDt) )

## get the common interval
c(max(a$u), min(a$v))

# [1] "2020-08-02" "2020-08-04"

HTH,
Eric


On Fri, Aug 21, 2020 at 12:34 PM Rasmus Liland <jral using posteo.no> wrote:

> On 2020-08-21 09:03 +0200, Dr Eberhard Lisse wrote:
> > Hi,
> >
> > I have a small test sample with lab
> > reports (PAP smears) from a number of
> > different providers.  These have
> > Collection Dates and the relevant
> > columns glimpse() something like
> > this:
> >
> > $ Provider       <chr> "Dr C", "Dr D", "Dr C", "Dr D"
> > $ CollectionDate <chr> "2016-11-03", "2016-11-02", "2016-11-03",
> "2016-11-03"
> >
> > I am looking to find (filter) the
> > reports which were collected in the
> > time period common to all providers?
> >
> > Something like
> >
> >        the largest First Common CollectionDate
> > and
> >        the smallest Last Common CollectionDate
> >
> > How would I do that?
> >
> > I can of course do this "manually", ie
> > collect all Providers and their first
> > and last Collection dates and then
> > find the Common First and Last one,
> > but wonder if there is an elegant way
> > of doing this :-)-O
>
> Dear Eberhard,
>
> Is each report in a csv file with those
> two columns, and you want to unify them
> into a dataframe with CollectionDate
> along the rows, and other details for
> each provider along the columns?  This
> can be done with various apply calls and
> reshape.  Can you please subset some
> more example data here using dput.  It
> makes it so much easier.
>
> /Rasmus
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