title: R extract values from each dataframe in multiple lists
body: <p>I'm working in R and have the following situation:
  10 lists of each 20 dataframes. The dataframes all have the same number of rows and columns. </p>
  
  <p>Now I want to extract from each dataframe in each list a value. This is a value from column name 'A' from the row where column 'B' equals 3. So using the example below (which represents one data frame), I would need to extract the value 8</p>
  
  <pre><code>A    B    C
  0    1    0
  1    2    0
  8    3    0
  </code></pre>
  
  <p>I want to store the values from all dataframes in a list in a vector.</p>
  
  <p>I found the following code in another question on this forum</p>
  
  <pre><code>List &lt;- list(c(1:3,4:5), c(4:6), c(7:9))
  lapply(List, '[[', 3)  # This retuns a list with only the third element
  unlist(lapply(List, '[[', 3)) # This retuns a vector with the third elements
  </code></pre>
  
  <p>So I want this to work with lists that contain dataframes, not just values. </p>