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Tim
> I am a newbee and convinced I must being doing something wrong. Appreciate
> your comments or thoughts
Here below is the text of my post at StockCentral on the issue. The link
is...
http://www.stockcentral.com.au/forum/machine/Forum32/HTML/000414.html
Roy
>From the number of questions that I have seen posted recently about
exploration events not coinciding with charted events I thought it might be
useful to discuss further the major cause of the problem, and to identify
many of the MetaStock functions that can contribute to it.
The problem does not lie with the MetaStock formula language but with the
way that individual users set up their explorations.
There seems to be a general lack of understanding, even among experienced
users, that EXPONENTIAL moving averages require much more data than the
"PERIODS" value of any affected function will supply. When using the
Explorer with the "Minimum Periods" option set we need to be aware that the
number of records explored will not exceed the highest "PERIODS" value used
in the active exploration formulas.
An EMA displayed on a chart has access to ALL loaded data, regardless of the
"PERIODS" value of the indicator. However an exploration will only have
access to the amount of data that the user has specified. The point to
remember with an exponential MA is that new data is added with each bar, but
old data is never dropped out (as happens with a simple MA). The old EMA
data becomes less significant with each new bar but it continues to be a
component of the final EMA value. This is the essential factor that causes
differences between chart and exploration values.
Quite a number of MetaStock functions use internal smoothing, and this is
usually (but not always) exponential in nature. Some functions allow user
control over the smoothing method employed, Mov() being an obvious example.
The following list cannot be guaranteed as 100% accurate but these are the
MS functions to watch out for that appear to use, or are in themselves, a fo
rm of exponential smoothing.
adx()
adxr()
atr()
bbandbot()
bbandtop()
dema()
dx()
emv()
forecastosc()
imi()
inertia()
macd()
mass()
mdi()
mov()
oscp()
oscv()
pdi()
pfe()
projosc()
qstick()
rangeindicator()
rmi()
rvi()
sar()
stoch()
tema()
trix()
wilders()
When using any of these functions in an exploration the accuracy of the
reported results will require the number of records explored to be set
appropriately. As a rule of thumb I would suggest multiplying the highest
"PERIODS" value by a factor of 5.
Another trick that should force the exploration to include the required
minimum number of records without actually specifying that number is to add
the following code to the filter and adjust "PERIODS" to a suitable value.
" AND Mov(C,PERIODS,S)>0"
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