tick data and one minute bar data appear out of line (IBrokers)

Hi Joshua

Just trying to follow that comment 'If you look at the tick data versus the
high-low range, you should see that all the tick prices fall within that
range for every aggregate interval.'

The summary of the two datasets is:

 summary(bars)
     Index                       CBA.Close
 Min.   :2016-03-03 10:06:00   Min.   :48.31
 1st Qu.:2016-03-03 11:37:00   1st Qu.:48.38
 Median :2016-03-03 13:08:00   Median :48.45
 Mean   :2016-03-03 13:08:00   Mean   :48.46
 3rd Qu.:2016-03-03 14:39:00   3rd Qu.:48.53
 Max.   :2016-03-03 16:10:00   Max.   :48.73


and

summary(ticks)
   Min. 1st Qu.  Median    Mean 3rd Qu.    Max.
  47.82   48.41   48.44   48.47   48.49   49.00

Now that min figure is the result of some market closing phenomena and it
really never went much below 48.3 so yes its true that they have a similar
range and min and max but ticks gets up into the just under 49.0 level
around 10:15 and bars only gets to that level around 11:30 and again at noon
while ticks is under 48.6 at that point.

Sounds like you don't think there is anything that unusual in the two
datasets so I guess I had better take that on board and keep on trying to
make this work.

Thanks for looking at it

Stephen Choularton PhD, FIoD


On 4/03/2016 2:50 PM, Joshua Ulrich wrote:

On Thu, Mar 3, 2016 at 9:38 PM, Stephen Choularton
<stephen at organicfoodmarkets.com.au> wrote:

Hi

I have been working on the spread between Commonwealth Bank (CBA.ASX) and
National Australia Bank (NAB.ASX).

I was a bit confused by the performance of my dealing loop so I took out
the
spread movement from rqHistoricData 1 minute bars using the close and
plotted it and also the spread derived from the tick data from reqMktData
which is being used to drive my dealing algorithm.

They are in the same ballpark but really rather different.  The graph
shows
the position best and can be viewed at this url:
http://www.organicfoodmarkets.com.au/bar-n-tick-plots.pdf

The 1-minute close price is a (potentially very small) sample of all
the price changes that occur in a given minute interval.  The fact
that they're similar is likely because the price wasn't moving much
during the hours in your plot.  If prices were moving a lot, I
wouldn't expect them to be very similar at all.

If you look at the tick data versus the high-low range, you should see
that all the tick prices fall within that range for every aggregate
interval.

I am not experienced with this so I wondered if this sort of discrepancy
is
typical or am I just making a mess of it.  If they are typical so it
makes
setting trigger levels a bit difficult as mine are derived from bar data
but
implemented by tick data movement.  I'm surprised the tick data doesn't
fall
within the one minute bar so any comments would be of great interest.  Am
I
better to only work with tick data for example?

Stephen Choularton PhD, FIoD