RuntimeWarning: invalid value encountered in long_scalars
<p>I'm having an issue with modifying an array, by adding the percentage of each item compared to its row to a new matrix. This is the code providing error:</p>

<pre><code>for j in range(1,27):
        for k in range(1,27):
                let_prob[j,k] = let_mat[j,k]*100/(let_mat[j].sum())
</code></pre>

<p>I get the error:</p>

<blockquote>
  <p>RuntimeWarning: invalid value encountered in long_scalars</p>
</blockquote>

<p>I have tried rounding the denominator to no success.</p>