title: cowplot, ggplot; how to align vertically two plots
body: <p>I'm trying yo aling vertically two plots with cowplot but I can't and I don't know why:</p>
  <p>Code:</p>
  <pre><code>manufac_count &lt;-  mpg %&gt;%
    count(manufacturer) %&gt;% 
    mutate(ymax = cumsum(n),
           ymin = lag(ymax, n = 1, default = 0))
  
  model_count &lt;- mpg %&gt;%
    group_by(manufacturer) %&gt;%
    count(model) %&gt;%
    ungroup() %&gt;% 
    mutate(ymax = cumsum(n),
           ymin = lag(ymax, n = 1, default = 0))
  
  p1 &lt;- ggplot(manufac_count) +
    geom_rect(aes(xmin = 2,
                  xmax = 3,
                  ymin = ymin,
                  ymax = ymax,
                  fill = manufacturer),
              color = 'white') +
    geom_rect(data = model_count,
              aes(xmin = 3,
                  xmax = 4,
                  ymin = ymin,
                  ymax = ymax,
                  fill = model),
              color = 'white',
              show.legend = FALSE) +
    xlim(0 , 4) +
    coord_polar(theta = 'y' ) +
    theme(legend.position = 'none')
  
  p2 &lt;- ggplot(data = mpg,
        mapping =  aes(x = hwy)) +
    geom_histogram(
      binwidth = 3)
  
  plot_grid(p1, p2, align = 'v', nrow = 2, ncol = 1)
  </code></pre>
  <p><a href="https://i.stack.imgur.com/ULrot.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/ULrot.png" alt="Plot" /></a></p>
  <p><strong>Question</strong></p>
  <p>How can I align the two plots vertically using cowplot or another library in R?
  or maybe I should convert the graphics to some other class?</p>