```
df <- data.frame(x = 1:3, y = 5:7)
## Not run: ## Error:
# as.vector(data.frame(x = 1:3, y = 5:7), mode = "numeric")
# ## End(Not run)
x <- c(a = 1, b = 2)
is.vector(x)
as.vector(x)
all.equal(x, as.vector(x)) ## FALSE
###-- All the following are TRUE:
is.list(df)
! is.vector(df)
! is.vector(df, mode = "list")
is.vector(list(), mode = "list")
```

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