title: Selectively negate elements in an array
body: <p>I am looking for some help around 'how to selectively negate the values of an array' in numpy.</p>
  
  <p>Already tried, <code>numpy.where()</code> and <code>numpy.negative</code> but not able to implement condition on selected few.</p>
  
  <pre><code>import numpy as np
  
  arr=np.arange(11)
  arr
  </code></pre>
  
  <hr>
  
  <pre><code>array([ 0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10])
  </code></pre>
  
  <p>Say I want to just negate all elements of the array that are between 2 and 8</p>
  
  <pre><code>array([ 0,  1,  2,  -3,  -4,  -5,  -6,  -7,  8,  9, 10])
  </code></pre>