[R] Extracting portions of one vector to create others

[Rui Barradas]

On 9/1/2025 3:09 PM, Paul Zachos wrote:
> Dear Colleagues,
> 
> I have a vector which indicates membership of subjects in one of 5 Classes
> 
> Beth$CLASS
>   [1] 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2
> [37] 2 2 2 2 2 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 7 7 7 7 7 7 7 7 7 7 7
> [73] 7 7 7 7 7 7 7 7 7 9 9 9 9 9 9 9 9 9 9 9 9 9 9 1
> 
> For purposes of an analysis (using linear models based on Ward and Jennings) I would like to create 5 new vectors
> 
> The values in vector CLASS1 will be ‘1’ if the corresponding value in Beth$CLASS is equal to ‘1’; ‘0’ otherwise
> 
> The values in vector CLASS2 will be ‘1’ if the corresponding value in Beth$CLASS is equal to ‘2’; ‘0’ otherwise
> 
> The values in vector CLASS4 will be ‘1’ if the corresponding value in Beth$CLASS is equal to ‘4’; ‘0’ otherwise
> 
> The values in vector CLASS7 will be ‘1’ if the corresponding value in Beth$CLASS is equal to ‘7’; ‘0’ otherwise
> 
> The values in vector CLASS9 will be ‘1’ if the corresponding value in Beth$CLASS is equal to ‘9’; ‘0’ otherwise
> 
> How would I go about this using R
> 
> Thank you
> _________________
> Paul Zachos, PhD
> Director, Research and Evaluation
> Association for the Cooperative Advancement of Science and Education (ACASE)
> 110 Spring Street  Saratoga Springs, NY 12866  |
> paz using acase.org  |  www.acase.org
> 
> 
> 
> 
> 
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> 
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Hello,

Here is a way. This creates a matrix with the vectors you ask for.
But it doesn't create 5 different vectors, it keeps them in one object 
only, a matrix.



CLASS <-
   c(1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L,
     1L, 1L, 1L, 1L, 1L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L,
     2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 4L, 4L, 4L, 4L, 4L, 4L,
     4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 7L, 7L,
     7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L,
     7L, 7L, 9L, 9L, 9L, 9L, 9L, 9L, 9L, 9L, 9L, 9L, 9L, 9L, 9L, 9L, 1L)
Beth <- data.frame(CLASS)

eq <- c(1, 2, 4, 7, 9)
res <- sapply(eq, \(x) as.integer(x == Beth$CLASS))
colnames(res) <- paste0("CLASS", eq)
head(res)
#>      CLASS1 CLASS2 CLASS4 CLASS7 CLASS9
#> [1,]      1      0      0      0      0
#> [2,]      1      0      0      0      0
#> [3,]      1      0      0      0      0
#> [4,]      1      0      0      0      0
#> [5,]      1      0      0      0      0
#> [6,]      1      0      0      0      0


If you really want 5 different objects in the global environment, you 
can use ?list2env.
This is not a good practice, you will have related, loose objects in the 
globalenv, making your code harder to debug. Keep it simple.


as.data.frame(res) |>
   list2env(envir = .GlobalEnv)
#> <environment: R_GlobalEnv>

CLASS1
#>  [1] 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0
#> [39] 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0
#> [77] 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1
CLASS2
#>  [1] 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 
1 1 1 1 1 1
#> [39] 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0
#> [77] 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0


Hope this helps,

Rui Barradas