Can someone explain MT4 EMA calulations

hi,


I would like to understand why does MT4 draw an EMA line from the very First bar.

I always thought like other MA's there must be some calculation points before the first EMA is finally calculated.

Look at the pic below:

I reduced on purpose the Bars in the Chart to 35 so to see all there is: applied are Mas(21) all 4 MT4 types.

as you see: only the Aqua (EMA) starts from the very first point.

According to other resources The first EMA should be starting later.

http://fxtrade.oanda.com/learn/forex...moving-average ( you are calculating your first EMA value where there is no previous day’s EMA, use SMA instead.)

http://stockcharts.com/school/doku.p...oving_averages
(An exponential moving average (EMA) has to start somewhere so a simple moving average is used as the previous period's EMA in the first calculation.)

Mainly I'm asking because I tried iMAOnArray with only a selected numbers of bars: the results are not usable



There are also discrepancies with the SMMA.


Only SMA and LWMA seems to be doing as I expected it.


Thanks

When writing custom indicators, one can set where the indicator should start drawing: SetIndexDrawBegin( int index, int begin)
http://docs.mql4.com/customind/SetIndexDrawBegin

Guess they don't bother to do it with the internal MA indicators.

MJ,

Your StockCharts link explains the underlying calc for EMA very well.

You'd need to ask MetaQuotes why they programmed MT4 in the way that they did. However, the aqua line doesn't appear to be plotting any kind of MA through the first few points, assuming that the only data it uses are the candle close points shown on your chart. Hence I suspect that, despite your setting the max number of bars to 35, it somehow has bars in the history older than 35 periods, that it's using in the calculation.

If you like MAs, then you might find the attached indy interesting.

David

Thanks hanover,

Well, I finally ended up to use 9 times the MAPeriod as Pre-Calculation size - using a customary calculation and not MT4 built-in options.