title: Select only matching files using multiple patterns in list.files
body: <p>I have the following csv files and I only want to select the ones which have matching 'pop' and 'throughput' values in each string:</p>
  
  <pre><code>example_pop_high_throughput_high_strategy.csv
  example_pop_high_throughput_base_strategy.csv
  example_pop_high_throughput_low_strategy.csv
  example_pop_base_throughput_high_strategy.csv
  example_pop_base_throughput_base_strategy.csv
  example_pop_base_throughput_low_strategy.csv
  example_pop_low_throughput_high_strategy.csv
  example_pop_low_throughput_base_strategy.csv
  example_pop_low_throughput_low_strategy.csv
  </code></pre>
  
  <p>I want only these:</p>
  
  <pre><code>example_pop_high_throughput_high_strategy.csv                
  example_pop_base_throughput_base_strategy.csv
  example_pop_low_throughput_low_strategy.csv
  </code></pre>
  
  <p>I can use list.files to select all files with, for example, 'high':</p>
  
  <pre><code>file_names &lt;- list.files("made/up/path", pattern = c("high"))
  </code></pre>
  
  <p>Although, trying to do this twice to just match 'high' and 'high', didn't work:</p>
  
  <pre><code>file_names &lt;- list.files("made/up/path", pattern = c("high", "high"))
  </code></pre>
  
  <p>Is there a way to select the files with matching 'pop' and 'throughput' values, preferably in a single expression?</p>