title: How to get rid of horizontal white lines appear out of nowhere in ggplot barplot?
body: <p><a href="https://i.stack.imgur.com/tVxUX.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/tVxUX.png" alt="enter image description here" /></a></p>
  <p>I'm using ggplot and I get those weird horizontal lines out of geom_bar. I cannot provide a minimal working example: the same code works with few observations and it relies on data I am importing and transforming. However, I can show the relevant line of codes and cross my fingers someone ran into this issue:</p>
  <pre><code>ggplot(data) + geom_bar(aes(x=Horizon, y=Importance, fill=Groups),
                             position='fill', stat='identity') +
  theme_timeseries2() +
  scale_fill_manual(values=c('#1B9E77', 'orange2', 'black', 
                             'red2', 'blue4')) +
  xlab('') + ylab('')
  </code></pre>
  <p>My personal function, <code>theme_timeseries2()</code> isn't the source of the problem: it happens even if I stop after geom_bar. I checked for missing values in <code>Importance</code> and every other column of my data frame and there are none.</p>
  <p>It's also very odd: the white lines aren't the same on the zoomed page as in the plot window of RStudio. They do print in .png format when I save the file, so there really is something going on with those horizontal bars. Any theory about why <code>geom_bar()</code> does this would be highly appreciated.</p>