title: Find last value in numpy array
body: <p>I have a 1d array and want to find the last value like this.</p>
  
  <pre><code>a = np.array([1,2,3,4,5,6,7,8,9,8,7,6,5,4,3,2,1])
  # find the index that value(7) last appear.
  np.argwhere(a &gt;= 7).max()
  # output 10
  </code></pre>
  
  <p>But it's suit for 1d array and how about 3d array.</p>
  
  <pre><code>b = np.tile(a.reshape(15,1,1), reps=(1,30,30))
  # now b is 3d array and i want to use same way to the axis = 0 in 3d array.
  np.argwhere(b &gt;= 7)
  # return a 2d array. It's not what i need.
  </code></pre>
  
  <p>Although I could use 'for' loop the other axis, but I want to solve it efficiently by numpy.</p>