Multi tool use

Creating an array with data conditional on another matrix

I know there must be an apply function or ave for this, but I am not quite sure how to do it:

I have data:

date player market
1: 1-1 1 1
2: 1-1 2 1
3: 1-1 1 2
4: 1-2 2 1
5: 1-2 3 2
6: 1-3 21 1
7: 1-4 1 1
8: 1-4 51 1
9: 1-4 1 1
10: 1-5 1 2


I also have a blank array, which has unique dates on the rows, unique markets on the columns, and unique players for the third dimension.

1
[,,1]
1 2
1-1
1-2
1-3
1-4
1-5


2
[,,2]
1 2
1-1
1-2
1-3
1-4
1-5


etc


I want to fill out the array with from the data.
I want each point to = 1 if the guy has an entry in the data where he is present for a date and market combination, and 0 if not. So for example, for 1 and 2, they would be filled out as:

1
[,,1]
1 2
1-1 1 1
1-2 0 0
1-3 0 0
1-4 0 1
1-5 0 1


2
[,,2]
1 2
1-1 1 0
1-2 1 0
1-3 0 0
1-4 0 0
1-5 0 0


Looping is out of the question. Thank you for your help.

1 Answer
1

You can use xtabs for this purpose. Where temp dates, Month market and day player.

xtabs

data(airquality)
tab<-xtabs(~Temp+Month+Day,airquality)

> dim(tab)
[1] 40 5 31


> str(tab)
xtabs [1:40, 1:5, 1:31] 0 0 0 0 0 0 0 0 0 0 ...
- attr(*, "dimnames")=List of 3
..$ Temp : chr [1:40] "56" "57" "58" "59" ...
..$ Month: chr [1:5] "5" "6" "7" "8" ...
..$ Day : chr [1:31] "1" "2" "3" "4" ...
- attr(*, "class")= chr [1:2] "xtabs" "table"
- attr(*, "call")= language xtabs(formula = ~Temp + Month + Day, data = airquality)


edit:
converting to data frame.

> head(as.data.frame(tab))
Temp Month Day Freq
1 56 5 1 0
2 57 5 1 0
3 58 5 1 0
4 59 5 1 0
5 61 5 1 0
6 62 5 1 0


as.data.frame(tab)

data.table

library(data.table); tab1<-as.data.table(tab); tab1

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