I'm searching but still can't find an answer to a quite simple question - how can we produce a simple dot plot of one variable with ggplot2 in R? 

with `plot` command this is very simple:

```
plot(iris$Sepal.Length, type='p')

```

But when I'm trying to pass one variable to qplot and specifying geom="point", I'm getting an error "Error in UseMethod("scale\_dimension")". 

![Simple one-variable plot](https://i.stack.imgur.com/66LrH.png)

How can we make a plot like this but with ggplot2?