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These two formulas give *exactly* the same result. They will only
differ due to rounding, and then the simpler one will be more
accurate. *Both* of them will never go negative.
The idea of the former is to calculate (baseless) percentage changes
and apply that to 100 (or 1000 or whatever) while the idea of the
latter is to rescale so that the value at BeginYearPx is equal to 100
(or whatever). I guess you ran into the negative values with the
percentage change idea where it can easily happen.
Not that it matters that much as, again, both give the same answer.
What matters is that neither will go negative.
Regards
MG Ferreira
TsaTsa EOD Programmer and trading model builder
http://www.ferra4models.com
http://fun.ferra4models.com
--- In equismetastock@xxxxxxxxxxxxxxx, "Larry Carhartt" <lc@xxxx> wrote:
> I originally tried as you suggest (not the same code as yours but
similar
> idea) and realized it does not work with negative numbers. The
parentheses
> make all the difference. The percent change is "added" to 100 to
make all
> the historical prices above zero. Simply multiplying by 100 allows the
> result to remain negative. Negative values will not plot in a bar or
> candlestick chart. For a line chart, what you suggest works fine since
> lines can display below zero.
>
> Thank you
>
> Best,
>
> Larry Carhartt
>
> MasterDATA
> The Only Source for Index & ETF Composite/Breadth Reports, Charts & Data
> www.MasterDATA.com
> lc@xxxx
> 818-701-6686
>
>
>
> -----Original Message-----
> From: equismetastock@xxxxxxxxxxxxxxx
[mailto:equismetastock@xxxxxxxxxxxxxxx]
> On Behalf Of mgf_za_1999
> Sent: Wednesday, September 28, 2005 8:17 PM
> To: equismetastock@xxxxxxxxxxxxxxx
> Subject: [EquisMetaStock Group] Re: Constant price from a specific
date -
> FOLLOWUP
>
>
> You could simplify the last line a bit, it now does something like
>
> x + calcs - x
>
> and you can simplify it to simply
>
> calcs
>
> Instead of
>
> 100+((C-BeginYearPx)/BeginYearPx*100)
>
> use
>
> 100 * C / BeginYearPx
>
> which is a lot easier to understand and change in future. The original
> version calculates the percentage change and applies that to 100
while this
> version simply rescales the close so that it is equal to 100 at the
> beginning of the year. Same result, but different approaches. One
looks like
> rocket science, other is a simple rescaling calculation.
>
> Anyhow, if you ever want to change it, say to start at 1,000 in stead of
> 100, or 1 or whatever, this is easier to do as well. Also, note how the
> ratio is being used here, to catch up on some other discussions.
>
> Regards
> MG Ferreira
> TsaTsa EOD Programmer and trading model builder
http://www.ferra4models.com
> http://fun.ferra4models.com
>
>
> --- In equismetastock@xxxxxxxxxxxxxxx, "Larry Carhartt" <lc@xxxx> wrote:
> > Thanks, Jose. I realize that. Because I publish these datafiles for
> > download, I didn't want users to have to download the full database
> every
> > night. By the setting the constant price to the last day of last
> year, they
> > only will be "required" to fully download once a year. Soon, instead
> > of doing a full download nightly, I am rewriting the plug-in so they
> will only
> > need to download the current day's data and it will put itself into
> > the right place in their file (append or replace). If I set the
> constant price
> > exactly one year ago, "all" the price values for the equal weighted
> prices
> > would change daily thus affecting the entire data base every day. I
> realize
> > the current relative price shown will be measure from the start
> price of the
> > current year. In terms of the overall price history, however,
> everything
> > stays aligned properly between stocks, indexes and ETFs. They are
all
> > reduced to a common denominator, 100.
> >
> > Best,
> >
> > Larry Carhartt
> >
> > MasterDATA
> > The Only Source for Index & ETF Composite/Breadth Reports, Charts &
> > Data www.MasterDATA.com lc@xxxx
> > 818-701-6686
> >
> >
> >
> > -----Original Message-----
> > From: equismetastock@xxxxxxxxxxxxxxx
> [mailto:equismetastock@xxxxxxxxxxxxxxx]
> > On Behalf Of Jose Silva
> > Sent: Wednesday, September 28, 2005 4:55 PM
> > To: equismetastock@xxxxxxxxxxxxxxx
> > Subject: [EquisMetaStock Group] Re: Constant price from a specific
> date -
> > FOLLOWUP
> >
> >
> > Larry, you've set the month variable in your code to last December, so
> > that currently it is only measuring the last ten months.
> >
> > To save a lot of time (and possible errors) with the date setting, you
> > could try Richard's excellent NexusDate.dll to automate this process
> > for you in MetaStock:
> >
> > ---8<------------------------
> > { Download NexusDate.dll from:
> > http://www.tradernexus.com/nexusdate }
> >
> > x:=ExtFml("NexusDate.DaysOld")>=366;
> > StartDate:=x=0 AND Alert(x,2);
> > BeginYearPx:=LastValue(ValueWhen(1,StartDate,C));
> >
> > 100+((C-BeginYearPx)/BeginYearPx*100)
> > ---8<------------------------
> >
> >
> > jose '-)
> > http://www.metastocktools.com
> >
> >
> >
> > --- In equismetastock@xxxxxxxxxxxxxxx, "Larry Carhartt" <lc@xxxx>
> > wrote:
> > >
> > > Although many of you supplied answers for my earlier inquiry
> regarding
> > > finding the price of 1 year ago and setting it as a constant (and I
> > > appreciate the response very much), I elected to use Roy Larsen's.
> > > For reasons that I will spare you, I now have decided to use
instead
> > > the last closing price of last year as the constant. In other
> words, I
> > > will be calculating the rate of return for the current calendar year
> > > both forward (this is normal practice) and backward (not very
common)
> > > based upon the closing price of the last trade day of last year. I
> > > modified Roy's formula as follows:
> > >
> > > Sm:=12;
> > > Sd:=28;
> > > Sy:=LastValue(Year()-1);
> > >
> > > StartDate:=(DayOfMonth()>=Sd AND
> > > Month()=Sm AND
> > > Year()=Sy);
> > >
> > > BeginYearPx:=LastValue(ValueWhen(1,StartDate,C));
> > >
> > > 100+(((C-BeginYearPx)/BeginYearPx)*100);
> > >
> > > I know it is more than a little modified, but Roy's original formula
> > > introduced me to some MetaStock functions I had never used before.
> > > THAT is the true value of this forum. Yes, you may get the exact
> > > answer you need, but you can learn from every answer (from guys like
> > > Roy, Jose, Richard and many more I should be mentioning). By the
> > > way, I still plan on using Roy's original formula for other
purposes
> > > (with full credit, of course). And, Jose, thank you for getting my
> > > brain kick-started by pointing out the problem with simply
> > > accumulating percentage gains/losses.
> > >
> > > When I use the above as the formula for the custom indicator, it
> > > generates the correct values. You may notice that I also modified
> the
> > > last line (my addition) so that the year always starts with a
> value of
> > > 100. The reason for this is that I plan on additionally generating
> > > OHLC MetaStock format price files outside of MetaStock and then
> > > converting those files to MetaStock (that code will be based on the
> > > same formula). That way, I can display bar or candlestick charts
> with
> > > the new "relative" OHLC prices. OHLC price files won't plot
> > > negative
> > > values, so starting at 100 always keeps the value above 0 even when
> > > going back previous to the beginning of the year or if the current
> > > price is down for the year. In other words, if the security is
> down 3%
> > > from the current year's beginning price, the displayed value for
> > > that
> > > day will be 97. It really seems to do a good job of keeping the
> > > displayed value properly aligned with the actual price and current
> > > rate of return without drift of any kind.
> > >
> > > I think I mentioned this before, but in case you are tuning in late,
> > > where I am really going with this is to recalculate all the indexes
> > > and ETFs I work with to equal weight composites. Most indexes are
> > > either cap weighted like the S&P 500 Index or price weighted
like the
> > > Dow Jones Industrial Average. To do that, I need to apply this
> formula
> > > to each of 3400 components I follow then recalculate the historical
> > > data on the composites using the values given by the above formula
> and
> > > then simply total them and divide by the number of components in the
> > > index or ETF. Voila, an equal weighted composite (I think or hope).
> > >
> > > Again, I appreciate everyone's input on this.
> > >
> > > Thank you.
> > >
> > > Best,
> > >
> > > Larry Carhartt
> > >
> > > MasterDATA Composite Plug-in For MetaStock
> > > The Only Source for Index & ETF Composite/Breadth Historical
> MetaStock
> > > Data <http://www.masterdata4metastock.com/>
> > > www.MasterDATA4MetaStock.com <mailto:lc@x...> lc@xxxx
> > > 818-701-6686
> >
> >
> >
> >
> >
> >
> >
> > Yahoo! Groups Links
>
>
>
>
>
>
> Yahoo! Groups Links
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