title: numpy array concatenation error: 0-d arrays can't be concatenated
body: <p>I am trying to concatenate two numpy arrays, but I got this error. Could some one give me a bit clue about what this actually means?</p>
  
  <pre><code>    Import numpy as np
      allValues = np.arange(-1, 1, 0.5)
      tmp = np.concatenate(allValues, np.array([30], float))
  </code></pre>
  
  <p>Then I got </p>
  
  <pre><code>ValueError: 0-d arrays can't be concatenated
  </code></pre>
  
  <p>If I do</p>
  
  <pre><code>    tmp = np.concatenate(allValues, np.array([50], float))
  </code></pre>
  
  <p>There is no error message but tmp variable does not reflect the concatenation either.</p>