title: Can you change the proportions of the ggplot2 graph from square to rectangle?
body: <p>I'm using <code>geom_segment</code> to plot a timeline of activity. It's all on the same line, and since I want to present it together with other graphs, I'd much rather make the y axis much smaller. It seems that the size of the gray graph area in ggplot2 is always square though, whether I scale it larger or smaller. Is there a way to say that I want x=500 y=50 or something like that?</p>
  
  <pre><code>df2 &lt;- structure(list(Activities =
                        structure(c(2L, 1L, 2L, 1L, 2L, 3L, 1L, 2L, 2L, 2L, 2L, 5L,
                                    4L, 3L, 2L, 2L), 
                                  .Label = c("authoring", "hacking", "learning", 
                                             "surfing", "tasks"), 
                                  class = "factor"), 
                        Start = c(14895L, 15005L, 16066L, 16226L, 16387L, 16394L,
                                  27030L,27532L, 27600L, 27687L, 28660L, 28713L, 
                                  29154L, 30264L, 30345L, 32245L), 
                        End = c(15005L, 16066L, 16226L, 16387L,16394L, 16509L, 
                                27491L, 27591L, 27628L, 28450L, 28704L, 29109L, 
                                30250L, 30345L, 31235L, 33794L)),
                   .Names = c("Activities", "Start", "End"), 
                   class = "data.frame", row.names = c(NA, -16L))
  a &lt;- 0:23
  </code></pre>
  
  <p>Here my plot:</p>
  
  <pre><code>ggplot(df2, aes(colour=Activities)) + 
    geom_segment(aes(x=Start, xend=End, y=0, yend=0), size=10) +
    scale_x_continuous(breaks=a * 60 * 60, labels=a) +
    xlab("Time") + ylab("") + 
    scale_y_continuous(breaks=NULL, limits=c(-.1, .1))
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/nEEKk.png" rel="noreferrer"><img src="https://i.stack.imgur.com/nEEKk.png" alt="Sample timeline chart"></a></p>