[R] Accessing Data Frame

[Ista Zahn]

Hi Benoit,

You can select rows from deck matched in aCard using

merge(deck, aCard)

Selecting rows that don't match is bit more difficult. You could do
something like

isin <- apply(mapply(function(x, y) x %in% y, deck, topCard),
               1,
               all)
deck[!isin, ]

perhaps.

Alternatively, you can use anti_join from the dplyr package:

library(dplyr)
anti_join(deck, topCard)

Best,
Ista

On Thu, Jan 3, 2019 at 10:38 AM Benoit Galarneau
<benoit.galarneau using polymtl.ca> wrote:
>
> Hi everyone,
> I'm new to the R world.
> Probably a newbie question but I am stuck with some concept with data frame.
> I am following some examples in the "Hands-On Programming with R".
>
> In short, how can I access/filter items in a data frame using a variable.
>
> One example consists of manipulating elements from a deck of card:
>
> > deck
>      face     suit value
> 1   king   spades    13
> 2  queen   spades    12
> 3   jack   spades    11
> 4    ten   spades    10
> etc.
>
> Let's say I want to remove or filter out the first card. I know I
> could do deck[-1].
>
> But let's say I have: topCard <- deck[1,]
>
> topCard is then a list of 3 elements
> > topCard
>    face   suit value
> 1 king spades    13
>
> My question is the following, how can I remove or filter out the deck
> using the topCard variable.
>
> In my programmer's head, something similar to this should "work":
> > deck[10,]
>     face   suit value
> 10 four spades     4
> > aCard <- deck[10,]
> > aCard
>     face   suit value
> 10 four spades     4
> > deck[aCard]
> Error in `[.default`(deck, aCard) : invalid subscript type 'list'
>
> Wihout having to specify all elements in the logical tests.
>
> deck[deck$face == aCard$face & deck$suit == aCard$suit & deck$value ==
> aCard$value,]
>     face   suit value
> 10 four spades     4
>
> ______________________________________________
> 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.