[R] Get data from a list of data frames

[Bert Gunter]

Well, just for giggles, Gerrit's solution can be easily vectorized (i.e. no
apply()-type stuff needed) IFF the structure of all the data frames are
identical so that rbind() works:

d <-do.call('rbind',Total[select.stat]) ## one data frame to combine them
all ;-)
d[d$sensor == 'thermometer','code']

Whether this is better, worse, or unneeded, I cannot say.

Cheers,
Bert


On Thu, Dec 15, 2022 at 6:11 AM Gerrit Eichner <
gerrit.eichner using math.uni-giessen.de> wrote:

> Hello, Stefano,
>
> maybe the following example contains what you want to achieve:
>
> Station1 <- data.frame(sensor = c("thermometer", "raingauge",
> "snowgauge", "anemometer"),
>                         code = c(2583, 1478, 3178, NA))
> Station2 <- data.frame(sensor = c("thermometer", "raingauge",
> "snowgauge", "anemometer"),
>                         code = c(2584, 1479, 3179, 4453))
> Station3 <- data.frame(sensor = c("thermometer", "raingauge",
> "snowgauge", "anemometer"),
>                         code = c(2584, 1479, 3179, 4453))
> Station4 <- data.frame(sensor = rev(c("thermometer", "raingauge",
> "snowgauge", "anemometer")),
>                         code = c(2584, 1479, 3179, 4453))
> Station5 <- data.frame(sensor = c("raingauge", "snowgauge",
> "thermometer", "anemometer"),
>                         code = c(2584, 1479, 3179, 4453))
>
> Total <- list("Station1"=Station1, "Station2"=Station2,
>                Station3 = Station3, Station4 = Station4,
>                Station5 = Station5)
>
> select.stat <- paste0("Station", c(1, 4, 5))
> select.sens <- "thermometer"
>
> sapply(Total[select.stat], function(x, sens)
>    x$code[x$sensor == sens], sens = select.sens)
>
>
>
>   Hth --  Gerrit
>
> ---------------------------------------------------------------------
> Dr. Gerrit Eichner                   Mathematical Institute, Room 212
> gerrit.eichner using math.uni-giessen.de   Justus-Liebig-University Giessen
> Tel: +49-(0)641-99-32104          Arndtstr. 2, 35392 Giessen, Germany
> http://www.uni-giessen.de/eichner
> ---------------------------------------------------------------------
>
> Am 15.12.2022 um 14:52 schrieb Stefano Sofia:
> > Dear R-list users,
> >
> > I have a list of n data frames built as follows:
> >
> >
> > Station1 <- data.frame(sensor = c("thermometer", "raingauge",
> "snowgauge", "anemometer"), code = c(2583, 1478, 3178, NA))
> > Station2 <- data.frame(sensor = c("thermometer", "raingauge",
> "snowgauge", "anemometer"), code = c(2584, 1479, 3179, 4453))
> > ....
> >
> > Total <- list("Station1"=Station1, "Station2"=Station2, ...)
> >
> > I would need to have a vector with the sensor codes of the thermometers
> of some stations, let's say of Station1, Station2 and Station5 (i.e.
> c(2583, 2584, 2587)).
> > I tried with lapply, but I have not been able to get what I need.
> > Could you please help me?
> >
> > Thank you
> >
> > Stefano
> >
> >
> >
> >           (oo)
> > --oOO--( )--OOo--------------------------------------
> > Stefano Sofia PhD
> > Civil Protection - Marche Region - Italy
> > Meteo Section
> > Snow Section
> > Via del Colle Ameno 5
> > 60126 Torrette di Ancona, Ancona (AN)
> > Uff: +39 071 806 7743
> > E-mail: stefano.sofia using regione.marche.it
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