Sample column from the data frame to be the same-CodePudding

Suppose I am generating a matrix of card, each has its own letter (A/B/C) and its own number (2-11).

Now I randomly sampled 5 cards.

card <- data.frame(
 pack = rep(c("A","B","C"), 10),
 rank = rep(2:11, 3)
) 

card

   pack rank
1     A    2
2     B    3
3     C    4
4     A    5
5     B    6
6     C    7
7     A    8
8     B    9
9     C   10
10    A   11
11    B    2
12    C    3
13    A    4
14    B    5
15    C    6
16    A    7
17    B    8
18    C    9
19    A   10
20    B   11
21    C    2
22    A    3
23    B    4
24    C    5
25    A    6
26    B    7
27    C    8
28    A    9
29    B   10
30    C   11

card[sample(seq_len(nrow(card)), 5),]

And then our sample is generated.

Now I have a question. Suppose I am generating a logical value, so that:

"TRUE when the pack letter of all the elements in the sample is the same. FALSE otherwise."

I have a heuristic idea about such one-line code:

I select the pack letter column in the data frame, then use the unique function to remove duplicate letters, and measure the number of entries of the removed-repetition column. If such number is one, then TRUE, FALSE otherwise.

But I forget how to select the pack letter column in the data frame and measure the number of entries of the removed-repetition column. Could anyone help?

I apologize for the lengthy passage.

CodePudding user response：

How about this?

length(unique(card[sample(seq_len(nrow(card)), 5),][,1])) == 1

#------------------------

a<-c()
for(i in 1:1000){
    a<-c(a,length(unique(card[sample(seq_len(nrow(card)), 5),][,1])) == 1)
}