Google sheets code for arrays - arrays

Question

I'm trying to get a code to work to calcualte average true range. So in the spreadsheet side I have
=getATR(GoogleFinance("stock", ʺallʺ, today()-60,today()))
And the code for the app is below. However I keep getting this TypeError: cannot set property "0.0" of undefined to "7.1". The line with the problem is the first instance where trurange[i][0] is called.
Appreciate your help with this, seems something silly on the syntax side.
function getATR(arr) {
var atr = 0;
var truerange = [];
var i=39;
for (var row = arr.length-1; row >= arr.length-40; row--) {
truerange[i][0] = arr[row][3] - arr[row][4];
truerange[i][1] = Math.abs( arr[row][3] - arr[row-1][2] );
truerange[i][2] = Math.abs( arr[row][4] - arr[row-1][2] );
truerange[i][3]= Math.max(truerange[i][0],truerange[i][1],truerange[i][2]);
i=i-1;
}
for(var row2 = 1; row2<40; row2++){
truerange[row2][4] = (truerange[row2-1][4]*13+truerange[row2][3])/14;
if(row2=39) {atr = truerange[row2][4]}
}
return atr;
}
Browser: ie9
Operating System: win7
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Answer 1

I am looking for a 6 day SMA of ATR. This code works for me
function getATR(arr) {
arr[1][9] = Math.abs( arr[1][2] - arr[1][3] )
for (var row = 2; row < 41; row++)
{
arr[row][6] = arr[row][2] - arr[row][3];
arr[row][7] = Math.abs( arr[row][2] - arr[row-1][4] );
arr[row][8] = Math.abs( arr[row][3] - arr[row-1][4] );
arr[row][9] = Math.max(arr[row][6],arr[row][7],arr[row][8]);
if (row>6) { arr[row][10] = (arr[row-5][9]+arr[row-4][9]+arr[row-3][9]+arr[row-2][9]+arr[row-1][9]+arr[row][9])/6 }
}
return arr[40][10];
}