title: Removing characters from multiple rows and multiple columns
body: <p>I have a dataset that contains 150k rows and 40 columns. The dataset consists of characters, strings as well as integers. I want to remove particular cells which contains a specific keyword/phrase that I want to remove.
  For example,
  If the initial dataset looks like</p>
  
  <pre><code>            A            B
   1)             1 | My name is Sam.
   2)         Hello | 2
   3)   Who are you | The water is green.
  </code></pre>
  
  <p>I want to remove the cell that contains the keyword "is". So that the final dataset will look like:-</p>
  
  <pre><code>            A            B
   1)             1 | NA
   2)         Hello | 2
   3)   Who are you | NA
  </code></pre>
  
  <p>The keyword can be in any format like a combination of strings or numbers or both.</p>