CODEWITHSUNDEEP
rcountdatasetcombinations
Siruphuhn
Siruphuhn

Reputation: 111

How to count combinations of elements in a data set?

I have an order data set in the following format:

Ordernumber; Category; # Sold Items
123; A; 3
123; B; 4
234; B; 2
234; C; 1
234; D; 5
...

So, every order has as many lines as there were different categories in the order.

Now, I want to count for every category pair how often they were ordered together in one order.

In the end I would like to have a "correlation" matrix like this

   A  B  C  D
A     1  
B  1     1  1
C     1     1
D     1  1

Has anyone a good (simple) idea?

Thank you so much!

Upvotes: 1

Views: 118

Answers (1)

user20650
user20650

Reputation: 25914

Perhaps using matrix multiplication gets you there:

dat <- read.table(header=T, text="Ordernumber; Category;  Sold Items
123; A; 3
123; B; 4
234; B; 2
234; C; 1
234; D; 5", sep=";")


tt <- table(dat[1:2])

crossprod(tt) # t(tt) %*% tt

#        Category
#Category  A  B  C  D
#       A  1  1  0  0
#       B  1  2  1  1
#       C  0  1  1  1
#       D  0  1  1  1

This has the diagonal but can easily be removed with diag

Upvotes: 1

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