title: ??? Input argument "x" is undefined
body: <p>I enter:</p>
  
  <pre><code>EDU&gt;&gt; %using the temporary variable levels
  EDU&gt;&gt; levels=range/quantise_range;
  levels=round(levels);
  quantisation_bits=log2(levels)
  </code></pre>
  
  <p>NB. There is no x variable anywhere</p>
  
  <p>My error is:</p>
  
  <pre><code>??? Input argument "x" is undefined.
  
  Error in ==&gt; range at 18
      y = max(x) - min(x);
  
  EDU&gt;&gt; %combining above process into one statement
  quantisation_bits=log2(round(range/quantise_range));
  ??? Input argument "x" is undefined.
  
  Error in ==&gt; range at 18
      y = max(x) - min(x);
  </code></pre>
  
  <p>Would someone care to explain thie issue? I am beginner into programming and I really don't understand how to read the error hint.</p>
  
  <p>Thanks.</p>
  
  <p>Additionally, in what may be due to whatever the same principle misunderstanding on my part is, I am finding trouble here with this code, with error also included:</p>
  
  <p>%Trying to create my own function, I’m pressing shift+enter at the end of lines for neatness:</p>
  
  <pre><code>EDU&gt;&gt; function what_am_i()
  disp 'I am a function'
  ??? function what_am_i()
      |
  Error: Function definitions are not
  permitted in this context.
  
  EDU&gt;&gt; 
  function what_am_i()
  disp' I am a function'
  ??? function what_am_i()    
      |
  Error: Function definitions are not
  permitted in this context.
  
  EDU&gt;&gt; end
  ??? end
      |
  Error: Illegal use of reserved keyword
  "end".
  </code></pre>