title: "The following object is masked _by_ .GlobalEnv" after using attach() in R
body: <p>I have a dataset of age named <em>hwk</em>. This dataset has attribute number, age, row, treatment. And I try to use <code>attach(hwk)</code> to put all private variables into global. However, it shows an error message about <code>attach(hwk)</code>. I wonder to know how can I solve this problem?
  <a href="https://i.stack.imgur.com/2JbOc.png" rel="nofollow noreferrer">the dataset of ages</a></p>
  
  <p><a href="https://i.stack.imgur.com/2HvoJ.png" rel="nofollow noreferrer">the error message</a></p>