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On Thursday, January 28, 1999 1:50 PM, Jim Osborn wrote:
>The "reference price" is the first tick of the day, stored as a
>thirty-two-bit unsigned number - LOTS of range there. All subsequent
>ticks are stored as signed sixteen-bit offsets from that reference.
>So, the most serious problem is an error in that reference price,
>because it affects every tick of the day. For word-length
>limitations to affect things, the difference from that initial tick
>would have to be plus or minus 32768 or greater.
I agree completely with what you indicate but I would like to clarify that
the 'plus or minus 32768 or greater' must take into account the price scale
used in the Symbol Universe. For instance, I had to change the scaling on
the INDU from 1/100 (plus or minus 327.68) to 1/10 (plus or minus 3276.8)
after the first 400 point daily Dow change dashed past the allowed limit and
blew the day of tick data. Likewise, most stocks are scaled to 1/1000 (plus
or minus 32.768) and I have been bitten a few times in the past by losing a
whole day of tick data due to the opening price being incorrect by more than
the scaling limit. I have never tried it but I suppose you could regain
historical tick data by rescaling the symbol in the Symbol Universe and then
pasting in tick data downloaded from the Omega Research ftp site.
Bob Scott
rlscott@xxxxxxxx
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