hadley/ggplot2 — Issue #416: limits of breaks in positional scales should be expanded
Author: kohske
Created: 2012-02-27 18:47:53+00:00
State: open

e.g.,

```
qplot(c(0.1, 1:5), 1:6)
```

This code will not show breaks at x = 0, but maybe it should show it unless the `limits` is set explicitly.

In the case of fill/colour legend, I changed to remove out-of-range value since the color/fill of oob value cannot be defined.
But we can assume the continuity the positional scale, so oob value can be defined.
Also, colour_gradient etc may have nicer breaks,
OR, limits should be pretty.

Maybe pretty limit will be preferable.
So, scales have two limits, limits of data and limits of the scale.
In the case of color/fill gradient or size, the limit of mapping is the limits of scale instead of the limits of data.