title: add symbol % to all the data frame in R
body: <p>I have a dataset like <code>mt.per &lt;- head(mtcars)</code> and I want to add <code>%</code> at the end of each cell value in all the dataset. many thanks in advance
  expected answer</p>
  <pre><code>                    mpg cyl disp  hp drat    wt  qsec vs am gear carb
      Mazda RX4         21.0%   6% 160% 110 % 3.90% 2.620% 16.46%  0%  1%    4% 4%
      Mazda RX4 Wag     21.0%   6%  160% 110% 3.90% 2.875% 17.02%  0%  1%    4% 4%
  ..... and so on
  </code></pre>