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    <p>The problem is with the initialization of your <code>abswidth</code>. You've done this</p> <pre><code>var absw1dth = [[]]; </code></pre> <p>...which will create an array with one element, another array with no elements. So when <code>e</code> is <code>1</code> (rather than <code>0</code>), the expression <code>absw1dth[e][0]</code> is trying to index into an array <code>abswidth[1]</code> that doesn't exist.</p> <p>If the data is as static as you've shown (there will always only be four rows in the <code>r0w</code> array), you could solve it with initialization:</p> <pre><code>var absw1dth = [ [], [], [], [] ]; </code></pre> <p>Now <code>abswidth</code> is a four-element array, where each element is an empty array.</p> <p>But if the data is more dynamic, I'd probably initialize on-the-fly:</p> <pre><code>var absw1dth = []; // Just an empty array for (e=0 ; e &lt; r0w.length ; e++ ) { abswidth[e] = []; // Create this element absw1dth[e][0] = ( r0w[e][7] + r0w[e][1] ); for (f=8 ; f &lt; r0w[e].length ; f++ ) { absw1dth[e][f - 7] = (r0w[e][f] + absw1dth[e][f - 8]); }; }; // ... } </code></pre> <p>If it's possible that code you're not showing may have already created the array elements within <code>abwidth</code>, but also may not have, you can test first:</p> <pre><code>var absw1dth = []; // Just an empty array for (e=0 ; e &lt; r0w.length ; e++ ) { if (!abswidth[e]) { abswidth[e] = []; // Create this element } absw1dth[e][0] = ( r0w[e][7] + r0w[e][1] ); for (f=8 ; f &lt; r0w[e].length ; f++ ) { absw1dth[e][f - 7] = (r0w[e][f] + absw1dth[e][f - 8]); }; }; // ... } </code></pre> <p>Or go all "functional programming" and use JavaScript's <a href="http://blog.niftysnippets.org/2008/02/javascripts-curiously-powerful-or.html" rel="nofollow">curiously-powerful <code>||</code> operator</a>:</p> <pre><code>var absw1dth = []; // Just an empty array for (e=0 ; e &lt; r0w.length ; e++ ) { abswidth[e] = abswidth[e] || []; // Create this element if needed absw1dth[e][0] = ( r0w[e][7] + r0w[e][1] ); for (f=8 ; f &lt; r0w[e].length ; f++ ) { absw1dth[e][f - 7] = (r0w[e][f] + absw1dth[e][f - 8]); }; }; // ... } </code></pre>
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    1. POCannot populate array within an array -- Javascript
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    1. UST.J. Crowder
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    1. COAwesome, awesome answer. I'd give this two votes if I could. I ended up using the first solution you provided, but find the other two very interesting. Saved that article for later, looks very handy.
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      1. USLars Markelson
    2. CO@Lars: LOL, glad that helped!
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    3. CO+1 for the curiously-powerful || operator
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      1. USVincent Mimoun-Prat
 

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