Find combinations in choose(k, n) in a R loop

user_15593366 0
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I need to find the SUM of all possible combinations in a set. For example:

sum(choose(5, 0),

    choose(5, 1),

    choose(5, 2),

    choose(5, 3),

    choose(5, 4),

    choose(5, 5))

Instead of writing it out like that, is possible to use a for loop to loop through choose() with any given n and k?

statistics r for-loop loops
2 Answers

You can use

> sum(choose(5, 0:5))
[1] 32

or just apply the binomial sums

> 2^5
[1] 32
user_121587570

In case you want to do this for more than just one n you can use sapply

setNames( sapply( 1:10, function(x) sum( choose( x, 0:x ) ) ), 1:10 )
   1    2    3    4    5    6    7    8    9   10 
   2    4    8   16   32   64  128  256  512 1024

Or using a for loop

res <- vector(l=10)
for(i in 1:10){ res[i] <- sum( choose( i, 0:i ) ) }
res
 [1]    2    4    8   16   32   64  128  256  512 1024
user_94620950
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