You are correct, the anti_join is working fine.
However, I still find it strange there is no "quick" way to find the
index of an item extracted from the data frame.
This works as it returns the deck without the card no 10.
aCard = deck[10,]
cardNo = which(deck$value == aCard$value & deck$suit == aCard$suit)
deck[-cardNo,]
But I'm still puzzled by the complexity of finding back the index of
the card with the long statement.
Another approach that "works" is the following, but I still find it
strange to depend on data frame row names to find the index:
cardNo <- as.numeric(row.names(aCard))
Apologies if the above question are strange. I'm coming C++ world with
some bias with objects. Again, since "aCard" is extracted from the
data frame, I assume (bias?) there would be a simple way to find back
the item in the data frame it came frame. Some kind of indexOf() or
similar on the container and item.
Benoit
Ista Zahn <istaz...@gmail.com> a écrit :
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.galarn...@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
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