8    63.0  1506391.0  5253154.0</span>
<span class="go">3 2015-06-19    73.0  1506391.0  5253154.0</span>
<span class="go">4 2015-06-18    88.5  1482760.0  5244669.0</span>

<span class="go">### Assign nan toplaces wherethe quality index is below 0.4</span>
<span class="gp">In [16]: </span><span class="n">ds2</span> <span class="o">=</span> <span class="n">ds</span><span class="p">[[</span><span class="n">grid_data_name</span><span class="p">]]</span><span class="o">.</span><span class="n">where</span>