title: How to change x-axis ticks to reflect another variable?
body: <p>I'm working with a data frame that includes both the day and month of the observation:</p>
  <pre><code>Day     Month      
  1      January
  2      January
  3      January
  ...
  32     February
  33     February
  34     February
  ...
  60     March
  61     March
  </code></pre>
  <p>And so on. I am creating a line graph in ggplot that reflects the day by day value of column <code>wp</code> (which can just be assumed to be random values between 0 and 1).</p>
  <p><a href="https://i.stack.imgur.com/1dgE6.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/1dgE6.png" alt="enter image description here" /></a>
  Because there are so many days in the data set, I don't want them to be reflected in the x-axis tick marks. I need to refer to the <code>day</code> column in creating the plot so I can see the day-by-day change in wp, but I just want month to be shown on the x-axis labels. I can easily rename the x-axis title with <code>xlab(&quot;Month&quot;)</code>, but I can't figure out how to change the tick marks to only show the month. So ideally, I want to see &quot;January&quot;, &quot;February&quot;, and &quot;March&quot; as the labels along the x-axis.</p>
  <pre><code>test &lt;- ggplot(data = df, aes(x=day, y=wp)) +
    geom_line(color=&quot;#D4BF91&quot;, size = 1) +
    geom_point(color=&quot;#D4BF91&quot;, size = .5) + 
    ggtitle(&quot;testex&quot;) +
    xlab(&quot;Day&quot;) +
    ylab(&quot;Value&quot;) +
    theme_fivethirtyeight() + theme(axis.title = element_text())
  </code></pre>