title: Select rows based on condition from each column
body: <p>I have data that I am analysing for a lab and I'm trying to use R for the first time.</p>
  
  <p>I've been reading about selecting rows based on conditions but I can't seem to find the way to do it for my data. </p>
  
  <p>I made a data frame and I didn't name the columns. Each column is a particular variant of a bacterial species that I am testing and its increasing values of OD/absorbance (in total 56 rows for each column) over a period of about 15 hours.</p>
  
  <p>I want to select the rows with values ranging from 0.2 to 0.4 from EACH column.</p>
  
  <p><img src="https://i.stack.imgur.com/26qIt.jpg" alt="A section of my data frame"></p>
  
  <p>So ideally I want something like:</p>
  
  <pre><code>   V1       V2
  9  0.2100  7 0.2181
  10 0.3017  8 0.3162
  11 0.4079  9 0.4137
  </code></pre>
  
  <p>etc.</p>
  
  <p>I guess I can select the rows manually from each column but there must be a quicker way.</p>
  
  <p>I then plan to calculate the mean of each column of the subset.</p>
  
  <p>Any help would be much appreciated, thanks!</p>