How to force a legend inside a plot to be horizontal and not vertical?

Question

I'd like the legend inside the plot to be horizontal (each one is beside each other not one is above the other) Is there a way to change from vertical to horizontal? Example: ``` mtcars$cyl <- factor(mtcars$cyl, labels=c("four","six","eight")) ggplot(mtcars, aes(x=wt, y=mpg, colour=cyl)) + geom_point(aes(colour=cyl)) + opts(legend.position = c(0, 1), title="Legend placement makes me sad") ```

Accepted Answer

You get horizontal legend by adding argument `legend.direction="horizontal"` inside the `theme()` or `opts()`

```
theme(legend.direction="horizontal")
```

Older versions

```
opts(legend.direction="horizontal")
```

How to force a legend inside a plot to be horizontal and not vertical?

Solution

Problem