Question

Basically I have a matrix and row with a in it I want to append a "1" to a list, otherwise append a "0"

The code is as follows:

is.there.A <- function(a,b,c,d,e) {

  library(combinat)
  x <- c(a,b,c,d,e)  
  matrix <- matrix(combn(x,3), ncol=3, byrow=T) 
  row <- nrow(matrix)
  list <- list()
  
  for (i in seq(row)) {

    if (matrix[i,] %in% "A") {c(list, "1")}

    else {c(list, "0")} 

    print(list)

    }

}

But it doesn’t work and this shows up.

Warning messages:

1: In if (matrix[i, ] %in% "A") { :

the condition has length > 1 and only the first element will be used

The question is how to overcome this to achieve the objective

Answer 1

You can avoid your explicit loop by using apply

is.there.A <- function(a,b,s,d,e) {

  library(combinat)
  x <- c(a,b,s,d,e)  
  .matrix <- matrix(combn(x,3), ncol=3, byrow=T) 

  any_A <- apply(.matrix, 1, `%in%`, x = 'A')
  as.list(as.numeric(any_A))

}

Never grow an object within a for loop, pre-allocate then fill.

Avoid naming objects with function names (eg c or matrix orlist)