subset a matrix by a expression with a column name

data<- matrix(c(1,2,3,4,5,6,7,8,9), nrow=3)

colnames(data) <- c("a", "b", "c")

How can we achieve the following for a matrix when the columnname (b) must be in the expression?
subset(data, b > 5)

Converting the matrix into a data.frame would work. But I am looking for a solution specifically for a matrix.

You cannot use subset with a matrix with names because columns are not stored as separate objects. A matrix is all just one vector with an extra dimension attribute. You would need to more explicit indexing. This will work

data[data[,"b"]>5,]

If you look at the subset.matrix function you can see it's just a wrapper to the [,] indexing operation. If you need the symbol b to work, you'd need to do the extra work to subset the data which is basically doing the same work as converting the data to a data.frame.

Do you mean this?

> data[data[, deparse(quote(b))] > 5, , drop = FALSE]
     a b c
[1,] 3 6 9

or

> subset.matrix(data, data[, deparse(quote(b))] > 5)
     a b c
[1,] 3 6 9

Note:

I would say, it is POSSIBLE to make it as what you asked for, but it would not be as simple as data[data[,"b"]>5,] for matrix data.