In our races, we adjust the PHRF rating of the non-spinnaker boats by 10% rounded up to the next multiple of 3. The base ratings are normally provided by a PHRF of the Chesapeake certificate. Is there a way to have the base rating in a competitor file and then have the rating for the race automatically adjusted based on Fleet?
Thanks,
Tom Owen
Tom,
YES - see below the note.
NOTE - What you are doing is probably the opposite of what you want to
do. Consider 2 boats rated 0 and 300. Your assumption is that the
0-rated boat doesn't get any slower without a spinnaker and the
300-rated boat gets slower by 30 sec/mi. That is the opposite of what a
naval architect will tell you. They would say that the absolute change
in speed is greater for faster boats than for slower boats, not less. It
might be a close approximation to use a fixed percentage, as you do, but
it would have to be applied differently. I haven't done any analysis but
you'd probably want to convert ratings to knots and apply the percentage
to knots and then convert back to ratings. It might be interesting and
fun to try coming up with a more accurate formula but that wasn't the
question you asked! [I note that folks often do stuff that doesn't
completely make sense based on "tradition" and the process is fully
accepted by everyone. I wouldn't want to "rock the boat" but if you were
starting from scratch I'd suggest alternative approaches to the problem.]
1. I suggest that using Excel to modify your base ratings in a ratings
file is arguably the best way to go. Then you have both sets of ratings
pre-set in a single file that you can print out and post if you want but
could also be used by Sailwave. Plus, writing the formula is simpler
than in Sailwave.
ROUNDUP((A1*1.1)/3,0)*3 [where "A1" is the reference to the base rating]
Using this method would show the non-spinnaker ratings for all purposes,
both the series and the races, in Sailwave.
2. There are 2 ways to do it in Sailwave depending on what you want to
show as the "rating" on the results.
a. Show base ratings on both series and races - If you want to show the
base rating then use a custom rating system formula under Setup|Scoring
system>Rating system. Check the custom checkbox near the bottom and then
input your custom formula on the "Custom rating system" tab. The base
rating will show but won't be used for scoring.
b. Show non-spinnaker ratings for races and base ratings for series - If
you want to show the rating actually used to score races then I suggest
using a pre-set ratings file generated with Excel. But, Sailwave can do
it. Under Tools|Assign personal handicaps you can assign a formula to
use to calculate ratings and define which classes the ratings will apply
to. You'll want to start with R1 (since you want it to apply to all
races) and you'll want to check the box to apply the same rating to all
subsequent races. On the series results the base rating will be shown
but on the results for each race the "personal" rating used to score
will be shown in the "rating" column.
WRITING THE SAILWAVE FORMULA
Excel has ROUND functions but I don't believe Sailwave does. So, you'll
essentially need to write your own. Sailwave does have an INT function
which takes the integer part of a number. So, for the personal handicap
calculation I think the logic (and formula) would be:
Base rating = default
Multiply by 110% = default*1.1
Divide by 3 = (default*1.1)/3
Add 0.9 for rounding up = ((default*1.1)/3)+.9
Take the integer value = int(((default*1.1)/3)+.9)
Multiply by 3 to get rating = int(((default*1.1)/3)+.9)*3
You can use the test expression button (the big sigma symbol) to try
different base ratings to confirm that the formula is doing what you
want. I tested this and got what you want for all positive ratings (I
didn't try any negative ratings as I don't really know how to apply your
method to those).
TRANSPARENCY
An important part of using ratings when scoring is transparency, meaning
that the reader has the information needed to easily do the calculations
and check the math. In that regard, the Custom rating system never shows
the ratings used to score races and thus is problematic. Personally, I
think I slightly prefer the Excel method because it makes posting a full
ratings list ahead of time easy and that promotes full transparency. The
Personal handicaps method gives the rating used in the race result
tables and the base rating in the series summary table. That provides
more information but because the ratings are different could cause
confusion and questions
Hope that helps to point you in the right direction.
Art
On 9/14/2014 5:51 AM, Tom OWEN towen999@msn.com [sailwave] wrote:
In our races, we adjust the PHRF rating of the non-spinnaker boats by 10%
rounded up to the next multiple of 3. The base ratings are normally
provided by a PHRF of the Chesapeake certificate. Is there a way to have
the base rating in a competitor file and then have the rating for the race
automatically adjusted based on Fleet?Thanks,
Tom Owen
Hi Tom,
In addition to Art’s extensive reply. Just an idea. Although you are using PHRF. I can’t see any reason why you couldn’t temporarily switch the scoring system to NHC custom external
Score it once and your custom template would set all the ratings then switch back to PHRF and score as normal
Jon
Jon Eskdale
07976 709777
Skype “eskdale”
On 14 September 2014 13:51, Tom OWEN towen999@msn.com [sailwave] sailwave@yahoogroups.com wrote:
In our races, we adjust the PHRF rating of the non-spinnaker boats by 10% rounded up to the next multiple of 3. The base ratings are normally provided by a PHRF of the Chesapeake certificate. Is there a way to have the base rating in a competitor file and then have the rating for the race automatically adjusted based on Fleet?
Thanks,
Tom Owen
Art,
Excellent suggestions! After my post, I did export a Competitor .csv file, imported into Excel, and then added a column that was labeled “Master PHRF”. I then created the actual PHRF to be used with standard Excel formulas. I can then import this into a new series, but not necessarily for individual races. This is essentially what you suggested as #1. I will most likely continue to do that since as you pointed out, transparency. However, I had not considered the Personal Handicaps and will do more investigation.
Thanks again for the analysis and very thoughtful insight.
Have a great day,
Tom
From: sailwave@yahoogroups.com [mailto:sailwave@yahoogroups.com]
Sent: Sunday, September 14, 2014 7:27 PM
To: sailwave@yahoogroups.com
Subject: Re: [sailwave] Rating Adjustments
Tom,
YES - see below the note.
NOTE - What you are doing is probably the opposite of what you want to
do. Consider 2 boats rated 0 and 300. Your assumption is that the
0-rated boat doesn’t get any slower without a spinnaker and the
300-rated boat gets slower by 30 sec/mi. That is the opposite of what a
naval architect will tell you. They would say that the absolute change
in speed is greater for faster boats than for slower boats, not less. It
might be a close approximation to use a fixed percentage, as you do, but
it would have to be applied differently. I haven’t done any analysis but
you’d probably want to convert ratings to knots and apply the percentage
to knots and then convert back to ratings. It might be interesting and
fun to try coming up with a more accurate formula but that wasn’t the
question you asked! [I note that folks often do stuff that doesn’t
completely make sense based on “tradition” and the process is fully
accepted by everyone. I wouldn’t want to “rock the boat” but if you were
starting from scratch I’d suggest alternative approaches to the problem.]
ROUNDUP((A1*1.1)/3,0)*3 [where “A1” is the reference to the base rating]
Using this method would show the non-spinnaker ratings for all purposes,
both the series and the races, in Sailwave.
a. Show base ratings on both series and races - If you want to show the
base rating then use a custom rating system formula under Setup|Scoring
system>Rating system. Check the custom checkbox near the bottom and then
input your custom formula on the “Custom rating system” tab. The base
rating will show but won’t be used for scoring.
b. Show non-spinnaker ratings for races and base ratings for series - If
you want to show the rating actually used to score races then I suggest
using a pre-set ratings file generated with Excel. But, Sailwave can do
it. Under Tools|Assign personal handicaps you can assign a formula to
use to calculate ratings and define which classes the ratings will apply
to. You’ll want to start with R1 (since you want it to apply to all
races) and you’ll want to check the box to apply the same rating to all
subsequent races. On the series results the base rating will be shown
but on the results for each race the “personal” rating used to score
will be shown in the “rating” column.
WRITING THE SAILWAVE FORMULA
Excel has ROUND functions but I don’t believe Sailwave does. So, you’ll
essentially need to write your own. Sailwave does have an INT function
which takes the integer part of a number. So, for the personal handicap
calculation I think the logic (and formula) would be:
Base rating = default
Multiply by 110% = default1.1
Divide by 3 = (default1.1)/3
Add 0.9 for rounding up = ((default1.1)/3)+.9
Take the integer value = int(((default1.1)/3)+.9)
Multiply by 3 to get rating = int(((default*1.1)/3)+.9)*3
You can use the test expression button (the big sigma symbol) to try
different base ratings to confirm that the formula is doing what you
want. I tested this and got what you want for all positive ratings (I
didn’t try any negative ratings as I don’t really know how to apply your
method to those).
TRANSPARENCY
An important part of using ratings when scoring is transparency, meaning
that the reader has the information needed to easily do the calculations
and check the math. In that regard, the Custom rating system never shows
the ratings used to score races and thus is problematic. Personally, I
think I slightly prefer the Excel method because it makes posting a full
ratings list ahead of time easy and that promotes full transparency. The
Personal handicaps method gives the rating used in the race result
tables and the base rating in the series summary table. That provides
more information but because the ratings are different could cause
confusion and questions
Hope that helps to point you in the right direction.
Art
On 9/14/2014 5:51 AM, Tom OWEN towen999@msn.com [sailwave] wrote:
In our races, we adjust the PHRF rating of the non-spinnaker boats by 10%
rounded up to the next multiple of 3. The base ratings are normally
provided by a PHRF of the Chesapeake certificate. Is there a way to have
the base rating in a competitor file and then have the rating for the race
automatically adjusted based on Fleet?Thanks,
Tom Owen