$ operator is invalid for atomic vectors

[Amy]

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[Pete Brecknock]

Amy

It would have been helpful if you had sent your R code of how you constructed the sab object.

If you have a data.frame, the subset command you are having trouble with should work fine. See below.

# Working Example
sab = data.frame(group=c('Group A', 'Group A', 'Group C', 'Group B', 'Group C'), gender=c(1,1,1,2,2))
subset(sab, sab$group=='Group A')

Perhaps your data is stored as a matrix? If so, the following code will fail with the error message you experienced.

# Non Working Example
sab2 = matrix(c('Group A', 'Group A', 'Group C', 'Group B', 'Group C',1,1,1,2,2),5,2)
subset(sab2, sab2$group=='Group A')

HTH

Pete