title: geom_path error while using ggplot to make a line chart with two lines
body: <p>I've created a dataframe by selecting columns from another dataframe, performed a few functions to get in the format I wanted then tried to use it to create a line plot with two lines (one for 2006, one for 2020). When I did, I got this error twice:</p>
  <blockquote>
  <p>geom_path: Each group consists of only one observation. Do you need to
  adjust the group aesthetic?</p>
  </blockquote>
  <p>I have tried:</p>
  <p>-ungrouping</p>
  <p>-adding &quot;group = YEAR&quot; or &quot;group = 1&quot; to aes()</p>
  <p>-switching the x-axis to a column with a numeric value</p>
  <p>Nothing worked.</p>
  <p>Results of dput(deaths_total):</p>
  <pre><code>structure(list(YEAR = c(2020L, 2020L, 2020L, 2020L, 2020L, 2020L, 
  2020L, 2020L, 2020L, 2020L, 2020L, 2020L, 2006L, 2006L, 2006L, 
  2006L, 2006L, 2006L, 2006L, 2006L, 2006L, 2006L, 2006L, 2006L
  ), month_num2 = c(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 1, 2, 
  3, 4, 5, 6, 7, 8, 9, 10, 11, 12), monthly_deaths = c(10L, 5L, 
  35L, 36L, 5L, 3L, 3L, 17L, 12L, 9L, 7L, 3L, 5L, 3L, 11L, 25L, 
  9L, 15L, 34L, 4L, 3L, 13L, 14L, 9L), month_name = c(&quot;January&quot;, 
  &quot;February&quot;, &quot;March&quot;, &quot;April&quot;, &quot;May&quot;, &quot;June&quot;, &quot;July&quot;, &quot;August&quot;, 
  &quot;September&quot;, &quot;October&quot;, &quot;November&quot;, &quot;December&quot;, &quot;January&quot;, &quot;February&quot;, 
  &quot;March&quot;, &quot;April&quot;, &quot;May&quot;, &quot;June&quot;, &quot;July&quot;, &quot;August&quot;, &quot;September&quot;, 
  &quot;October&quot;, &quot;November&quot;, &quot;December&quot;)), class = c(&quot;grouped_df&quot;, 
  &quot;tbl_df&quot;, &quot;tbl&quot;, &quot;data.frame&quot;), row.names = c(NA, -24L), groups = 
  structure(list(
  YEAR = c(2006L, 2020L), .rows = structure(list(13:24, 1:12), ptype = 
  integer(0), class = c(&quot;vctrs_list_of&quot;, 
  &quot;vctrs_vctr&quot;, &quot;list&quot;))), class = c(&quot;tbl_df&quot;, &quot;tbl&quot;, &quot;data.frame&quot;
  ), row.names = c(NA, -2L), .drop = TRUE))
  </code></pre>
  <p>Current Code:</p>
  <pre><code>deaths_graph2 &lt;- ggplot(deaths_total, aes(x = month_name, y = monthly_deaths, colour = YEAR)) 
  +
  geom_line()
  </code></pre>