CODEWITHSUNDEEP
r
Walker in the City
Walker in the City

Reputation: 587

And together columns of logical matrix together to get one vector

I want to take a logical matrix and and all of the columns in the matrix together to create a vector. An example:

a = c(TRUE, TRUE, FALSE, TRUE, FALSE, FALSE)
A = matrix(a, nrow = 3, ncol = TRUE, byrow = TRUE)

I would like to produce 

[1] TRUE  FALSE  FALSE

Currently I am doing this with 

apply(A, 1, function(x) Reduce('&', x))

However, this goes very slow with the size of my input, and I was wondering if there was a more efficient way to do this.

Upvotes: 0

Views: 20

Answers (2)

akrun
akrun

Reputation: 887078

Instead of using Reduce within apply, an option would be to either convert the 'A' to data.frame and then do

Reduce(`&`, as.data.frame(A))
#[1]  TRUE FALSE FALSE

Or split by col and then 

Reduce(`&`, split(A, col(A)))
#[1]  TRUE FALSE FALSE

Upvotes: 1

Lamia
Lamia

Reputation: 3875

It will be faster to use:

apply(A,1,all)

instead of a call to Reduce.

Also, the rowSums function is equivalent to apply(x,1,sum) but much faster, so it will probably be even faster to do:

rowSums(A)==ncol(A)

Upvotes: 1

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