title: How to filter a dataframe so that it finds the maximum value for 10 unique occurrences of another variable
body: <p>I have this dataframe here which I filter down to only include counties in the state of Washington and only include columns that are relevant for the answer I am looking for. What I want to do is filter down the dataframe so that I have 10 rows only, which have the highest Black Prison Population out of all of the counties in Washington State regardless of year. The part that I am struggling with is that there can't be repeated counties, so each row should include the highest Black Prison Populations for the top 10 unique county names in the state of Washington. Some of the counties have Null data for the populations for the black prison populations as well. for You should be able to reproduce this to get the updated dataframe.</p>
  <pre><code>library(dplyr)
  
  incarceration &lt;- read.csv(&quot;https://raw.githubusercontent.com/vera-institute/incarceration-trends/master/incarceration_trends.csv&quot;)
      
      blackPrisPop &lt;- incarceration %&gt;%
        select(black_prison_pop, black_pop_15to64, year, fips, county_name, state) %&gt;%
        filter(state == &quot;WA&quot;)
  </code></pre>
  <p>Sample of what the updated dataframe looks like (should include 1911 rows):</p>
  <pre><code>   fips   county_name state year black_pop_15to64 black_prison_pop
  130 53005 Benton County    WA 2001             1008               25
  131 53005 Benton County    WA 2002             1143               20
  132 53005 Benton County    WA 2003             1208               21
  133 53005 Benton County    WA 2004             1236               27
  134 53005 Benton County    WA 2005             1310               32
  135 53005 Benton County    WA 2006             1333               35 
  </code></pre>