title: Replace value in data frame if value is greater or smaller
body: <p>I have problem manipulating data-frame in R. This is basic thing in R, but I can't find best command to do this type of things.</p>
  
  <p>Dummy example</p>
  
  <pre><code>Var1 20 300  39
  Var2 49  23  91
  Var3  0 239 210
  </code></pre>
  
  <p>How can I replace value with <code>10</code> in column 2 if value is smaller than <code>10</code>;<br>
  Or how to replace all values in data-frame with <code>100</code>, if they are greater than <code>200</code>? </p>