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Fig & Shield Prices
http://www.classictw.com/viewtopic.php?f=13&t=21240
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Author:  Mad Mick [ Fri Dec 12, 2008 7:44 am ]
Post subject:  Re: Fig & Shield Prices

Great detective work EP!

I'm a bit uncomfortable with the value used for pi. Would you mind checking the following, using the correct value for pi ?:

Fig: =200+40*COS((NOW()-32142)*((2exp16 -1)/(2exp15-1))* pi /87.5)

Kav

Author:  ElderProphet [ Fri Dec 12, 2008 3:32 pm ]
Post subject:  Re: Fig & Shield Prices

Even such a small discrepancy as that diverges measurably as early as day 3. My formula is accurate to the sub-second from Dec 31, 1987, through leap-day, 2088. I'll post the screen cap later if I have time.

I realize that those values for Pi are the result of rounding errors in TW, but they are exact nevertheless.

Author:  the reverend [ Fri Dec 12, 2008 3:41 pm ]
Post subject:  Re: Fig & Shield Prices

ElderProphet wrote:
First Hold = 200 + 50 * Sin(X * 2Pi / 17.5), where Pi = 3.14146.
Fig Price = 200 + 40 * Cos(X * 2Pi / 87.5), where Pi = 3.13999.
Shield Price = 150 - 40 * Cos(X * 2Pi / 87.5), where Pi = 3.13999.


if you're uncomfortable with the bogus values of PI, just change the other constants:

First Hold = 200 + 50 * Sin(X * 2Pi / 17.5007387), where Pi = 3.1415926.
Fig Price = 200 + 40 * Cos(X * 2Pi / 87.5446586), where Pi = 3.1415926.
Shield Price = 150 - 40 * Cos(X * 2Pi / 87.5446586), where Pi = 3.1415926.

i think you get the same result...

Author:  ElderProphet [ Fri Dec 12, 2008 7:13 pm ]
Post subject:  Re: Fig & Shield Prices

Attachment:
LeapDay2088.jpg
LeapDay2088.jpg [ 112.01 KiB | Viewed 6619 times ]

I believe that says it all. Those are a mere 141 ms apart.

Rev, those decimal values would suffice, but would be .8 sec off after 100 years, far too great a discrepancy. :P

Author:  the reverend [ Fri Dec 12, 2008 7:42 pm ]
Post subject:  Re: Fig & Shield Prices

ElderProphet wrote:
Rev, those decimal values would suffice, but would be .8 sec off after 100 years, far too great a discrepancy. :P

yeah but you get my point - you're not changing the value of pi. you're just keeping your 17.5 and 87.5 numbers simple and fudging pi a little, but in the end its 2 * pi * someConstant.

Author:  Kemper__3 [ Fri Jan 02, 2009 11:08 pm ]
Post subject:  Re: Fig & Shield Prices

I was going to say something witty, but the medieval registration process of these forums has taken it out of me. I'll instead just say "hi."

Author:  Silence [ Sat Jan 03, 2009 4:50 pm ]
Post subject:  Re: Fig & Shield Prices

Hi Kemp!

if you mail that SG fool, he can give you your old account back :)

Author:  Admin 1 [ Sat Jan 03, 2009 4:55 pm ]
Post subject:  Re: Fig & Shield Prices

Silence wrote:
Hi Kemp!

if you mail that SG fool, he can give you your old account back :)


hey k3 hit me up email i'll get you all fixed up.

Author:  Kemper__3 [ Sun Jan 04, 2009 9:18 pm ]
Post subject:  Re: Fig & Shield Prices

I was just ended up here from some various random websurfing and thought I would say hi. No point in getting my old account back, I don't plan on hanging around. Nice to see some people still remember me :P

Author:  ElderProphet [ Mon Jan 05, 2009 8:12 pm ]
Post subject:  Re: Fig & Shield Prices

Ah, the legend himself... Hope you are doing well, and that you'll poke your head in and fight some of this mis-information from time to time.

Hope to see you again before another 2+ yrs go by.

+EP+

P.S. I'm interested in the witty remark that you didn't say.

Author:  RajuAbju [ Thu Jan 29, 2009 11:42 am ]
Post subject:  Re: Fig & Shield Prices

Elder, I've found the chart below which you created to be an invaluable resource for me. But I'm having a wierd issue coming up. I have my own excel spreadsheet which I use to keep track of planets, ports, figs, etc. I wanted to copy your chart into my existing spreadsheet, so as to have a single excel file with multiple sheets, simplifying things for myself.

So I select all from your chart, copy, and paste into a new blank sheet in my own spreadsheet. At first, everything goes fine. But, as soon as I close your chart, mine goes haywire with the dates. They change into numbers, starting at 39830, and increasing by 10 for each date. All the data appears to remain the same, its only the dates listed on the chart.

As soon as I reopen your chart, the dates go back to normal. Any idea what could be causing this, and any possible fix?

Screenshot is below



ElderProphet wrote:
Okay, so about those formulas...

In the formulas below, X is NOW - 32142. NOW is the number of days, including the fractional part, since 00:00:00 on Dec 31, 1900. 32142 is equivalent to 00:00:00 on Dec 31, 1987 (or 1999 in-game). The sine is calculated with X as a radian measurement.

The prices are always truncated for the display, but the real price includes the fractional part. You will be charged this hidden fractional amount.

First up is the Holds price. Review Traitor's formulas for calculating the cost for holds. The first hold cost (B in Traitor's formula) is calculated as follows:

First Hold = 200 + 50 * Sin(X * 2Pi / 17.5), where Pi = 3.14146.

And now for the important one, the Fig Price:

Fig Price = 200 + 40 * Cos(X * 2Pi / 87.5), where Pi = 3.13999.

And last but not least, Shield Price:

Shield Price = 150 - 40 * Cos(X * 2Pi / 87.5), where Pi = 3.13999.

In Excel:
Hold1: =200+50*SIN((NOW()-32142)*2*3.14146/17.5)
Fig: =200+40*COS((NOW()-32142)*2*3.13999/87.5)
Shield: =150-40*COS((NOW()-32142)*2*3.13999/87.5)


I'll post the scripts on Grimy in a few days.

I've attached an Excel spreadsheet to this post, that forecasts prices for 70 days from NOW, which will update each time you load it. A pic of the chart is below.

Regards,
+EP+

Attachment:
The attachment EP_HFS_Chart.jpg is no longer available


Attachments:
screenshot.JPG
screenshot.JPG [ 126.31 KiB | Viewed 6300 times ]

Author:  V'Ger [ Thu Jan 29, 2009 1:20 pm ]
Post subject:  Re: Fig & Shield Prices

Poodle,

The problem is that excel is not converting the date values to dates, but rather is keeping them as integers. If you look at the format option for the chart, you should be able to select dates rather than a number, which will cause excel to show it in the correct format.

Regards,
V

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