Backfilling data

Questions about MultiCharts and user contributed studies.
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Marina Pashkova
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Postby Marina Pashkova » 14 Feb 2008

Thank you for the suggestion Bob!

Nick
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Postby Nick » 15 Feb 2008

I guess the problem is that studies can reference previous values of themselves. So while it is possible to load bars 'backwards' for completely predictable results you need to calculate studies 'forwards'.

Having said that if 'maximum bars that study will reference' is used correctly it should be possible to plot studies correctly on recent bars once you have loaded that number of bars. I guess giving the user the option on a study by study basis is the answer.

Cheers,
Nick.

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RobotMan
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Postby RobotMan » 15 Feb 2008

I guess the reason I said what I did in the previous post is because, in one of my studies, I use a dual array that looks at the past 20 days of 5 minute data of both NYSE total volume and Nasdaq total volume. It does a statistical analysis, and compares it to the current 5 minute volume.
If I have to reload historical data from eSignal, then I need to wait until that finishes before the indicator starts doing it's thing or I get a "red square balloon" error and the indicator turns off.
I'm sure others do not use so intense of studies and would like to see the window fill up right away.

I always thought it would be nice if a little clock or bar graph to show progress, with a text message appeared in each chart window when it starts to let you know that it wasn't just "waiting for data" or "connecting" when in reality nothing was actually happening.
It would glow green if things were ok and red if there was a problem and had timed itself out. If it was green and taking a long time it might show a text message saying that eSignal's servers suck or that there is unusually high packet loss. If it turned red, the text message would tell me that it had timed out and to check my internet connection or data provider. It might even tell me to get off high bandwidth intermittent cable and go back to reliable rock solid DSL.
Anyway, I'm sure we are a long way from that yet.

Bob Perry
Los Altos, CA

drwar
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Postby drwar » 15 Feb 2008

[quote]I guess the problem is that studies can reference previous values of themselves. So while it is possible to load bars 'backwards' for completely predictable results you need to calculate studies 'forwards'.

Having said that if 'maximum bars that study will reference' is used correctly it should be possible to plot studies correctly on recent bars once you have loaded that number of bars. I guess giving the user the option on a study by study basis is the answer.

Cheers,
Nick.[/quote]

Nick that is not true when the study values are accumulative. If the study requires x bars back to do its next calculation and also figures in an accumulated value based on previous calculations its a problem. This is our situation.

J~

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Andrew Kirillov
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Postby Andrew Kirillov » 16 Feb 2008

Jerry is right. Lots of indicators will not be "normalized" even if you have enough bars. So you need to have days or maybe weeks of data. It depends on indicator. So It is safer to calculate studies on data loading complete.

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TJ
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Postby TJ » 16 Feb 2008

i.e. after the data is fully loaded, go turn off the indicator/strategy, then turn it on again (through status). So that the indicator/strategy can do its calculation from the very beginning of the data series.


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