title: Confuse about the result of my check null value code
body: <p>I tried this to check whether a row is null or not.</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code>package org.apache.spark.h2o.utils
  
  import water.fvec.{NewChunk, Frame, Chunk}
  import water._
  
  class Miss extends MRTask {
    override def map(c: Chunk, nc: NewChunk): Unit = {
      for (row &lt;- 0 until c.len()) {
        if(c.atd(row) == 0){  
         nc.addNum(0)
        }
        else
         nc.addNum(1)
      }
    }
  }</code></pre>
  </div>
  </div>
  </p>
  
  <p>And I can not understand the result of my code here</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code>           A    B    C    D            E   check
      min                                     0
     mean                                     0
   stddev                                     0
      max                                     1
  missing                                     0
        0  5.1  3.5  1.4  0.2  Iris-setosa    1
        1  4.9    3  1.4  0.2  Iris-setosa    1
        2  4.7  3.2  1.3  0.2  Iris-setosa    1
        3  4.6  3.1  1.5  0.2  Iris-setosa    1
        4    5  3.6  1.4  0.2  Iris-setosa    1
        5  5.4  3.9  1.7  0.4  Iris-setosa    1
        6  4.6  3.4  1.4  0.3  Iris-setosa    1
        7    5  3.4  1.5  0.2  Iris-setosa    1
        8  4.4  2.9  1.4  0.2  Iris-setosa    1
        9  4.9  3.1  1.5  0.1  Iris-setos...</code></pre>
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  </p>
  
  <p>In the code generate check column, Why my max row is 1? I'm new to h2oFrame, can anyone help me understand this? IS there something wrong with my code? Thx</p>