Scan Data / Chart Data

dhall6938

I have noticed several times over the last few months that my inter day scan results do not always match what my chart is telling me. Sometimes the scan will catch up to the chart within 15 min and at other times, it will not happen until after the close. I assume that SC is using different data sources. One for the scan and a different source for the updating charts? Maybe the scan uses the same data but processes it differently than the chart updates? Anyway, it's kind of frustrating and feels a bit strange to me.

markd

Here is Stockcharts' explanation of how the scan engine database is updated:

https://stockcharts.com/docs/doku.php?id=scans:intro

If your reports are correct, it may be that the scan engine is not dropping the initial data item in indicator calculations until after the close, but the chart engine does. But I'm just guessing.

dhall6938

Mark, thanks again. My experience does not match much of what they describe. As an example. I have never, not one time, seen my scan engine update at 8:31 as they say. It always takes about 4 minutes after the open to get an update different from the previous day's close. And, the other strange stuff that I already mentioned but it works fine about 90% of the time.

markd

Well, it says the first update *begins* at 9:31 eastern - it may take several minutes to *complete* the first update. I would guess the scan sees the "old" data until the update is completed.