BBands upper and lower bands incorrect if input too small

[hunglee]

I've tested with BTC-ADA data, it return 3 lines are the same data

var close = [ 0.00001467,
  0.00001465,
  0.00001466,
  0.00001467,
  0.00001466,
  0.00001471,
  0.00001474,
  0.0000147,
  0.00001469,
  0.00001469,
  0.0000147,
  0.00001471,
  0.00001476,
  0.00001472,
  0.00001472,
  0.0000147,
  0.00001473,
  0.00001473,
  0.00001471,
  0.0000147,
  0.00001469,
  0.00001469 ];
talib.execute({
                    name: "BBANDS",
                    inReal: close,
                    startIdx: 0,
                    endIdx: close.length - 1,
                    optInTimePeriod: 20,
                    optInNbDevUp: 2,
                    optInNbDevDn: 2,
                    optInMAType: 0
                }, function (err, result) {
if (err) {
                        console.log('error', err);
                    }
                    else {
                        console.log(result);
                    }

});

then the results

{ begIndex: 19, nbElement: 3, result: { outRealUpperBand: [ 0.000014700999999999999, 0.000014702, 0.000014703999999999997 ], outRealMiddleBand: [ 0.000014700999999999999, 0.000014702, 0.000014703999999999997 ], outRealLowerBand: [ 0.000014700999999999999, 0.000014702, 0.000014703999999999997 ] } }

[laserlance]

I bet if you change the optInTimePeriod to something smaller then you will see a difference. The issue you present is not unique to this wrapper; it is a feature of the underlying TA-LIB library of functions. If you don't give enough data, or if your optInTimePeriod is too high for the amount of data you present to the function, then you should not expect accurate results.