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#61
Ballistics / Re: Weapon Employment Zone
Last post by admin - June 30, 2014, 08:08:28 PM
Cool.

would it be possible to include the effects of a  hold over/under (and the horizontal equivalent)? (in combination with cant)
#62
Ballistics / Re: Weapon Employment Zone
Last post by mman - June 30, 2014, 05:16:20 PM
Thanks Robert! I made another WEZ tool based on monte carlo using your bfx_Rang random number.

Input values:



CEP based WEZ versus monte carlo based WEZ. Results for 4 different bullets/conditions.



+/- values for monte carlo are to show 95 % confidence interval which means that 95 % of the time error is less than that. To get that narrow confidence interval I had to calculate 100 000 simulations per bullet per range. It took 92 minutes while CEP tool did the same (and other calculations as well) in 7 sec. However CEP tool seems to give errors of 0 - 7 percentage points. As expected CEP tool is still most of the time good enough for comparison.
#63
Ballistics / Re: Weapon Employment Zone
Last post by admin - June 29, 2014, 02:40:13 PM
From Bfx_help(...)
90   ==========================Non volatile random numbers===========================
91   i is a positive integer number, b is the bottom value, t (>b) is the top value
92   <r> is an optional range
93   random_number = BfX_Ran(i; <r>) 0 <= random_number <= 1]
94   b <= random_number <= t = BfX_Ranb(i; b; t; <r>)
95   c and s are center and width of normal distribution
96   normal distribution b <= random_number <= t= BfX_Rang(i; c; s; b; t; <r>)
97   use <r> to link cells to guide Excels calculation order

i is the seed.

<r> is a cell or a range

B   C   D
2   seed   1234567
3      
4   0,051118901   =BfX_Ran(seed)
5   0,207298019   =BfX_Ran(seed;C4)
6   0,529684412   =BfX_Ran(seed;C5)
7   0,164931189   =BfX_Ran(seed;C6)
8   0,760708209   =BfX_Ran(seed;C7)
9   0,711878956   =BfX_Ran(seed;C8)
10   0,434484066   =BfX_Ran(seed;C9)
11   0,032066679   =BfX_Ran(seed;C10)
12   0,018770791   =BfX_Ran(seed;C11)
13   0,197369616   =BfX_Ran(seed;C12)
14      
15   bfx_ran    refers to the previous cell in order to force
16      a specific order of random number (cell) processing

My random number is non volatile.
Volatile means according to MS:
Excel supports the concept of a volatile function, that is, one whose value cannot be assumed to be the same from one moment to the next even if none of its arguments (if it takes any) has changed. Excel reevaluates cells that contain volatile functions, together with all dependents, every time that it recalculates. For this reason, too much reliance on volatile functions can make recalculation times slow. Use them sparingly.

The following Excel functions are volatile:

    NOW

    TODAY

    RAND

    OFFSET

    INDIRECT

    INFO (depending on its arguments)

    CELL (depending on its arguments)
#64
Ballistics / Re: Weapon Employment Zone
Last post by mman - June 28, 2014, 09:24:37 AM
Robert can you explain input values of your random number generators?
#65
Ballistics / Re: Weapon Employment Zone
Last post by admin - June 28, 2014, 12:05:12 AM
1) My random number generator generates the same output sequence for the same seed.
2) My random number generator is not recalculated if somewhere else on the spreadsheet an (unlinked) cell is recalculated.


#66
Ballistics / Re: Weapon Employment Zone
Last post by 375CT - June 27, 2014, 05:10:39 PM
Quote from: mman on June 27, 2014, 09:20:58 AM
Quote from: 375CT on June 27, 2014, 08:36:48 AM
Makes sense, but how to be sure? I get and agree to the point you made, but making no sense, well, that's the hard part out of this, because we are not dealing with any way to test the actual implementation.

Litz speaks about standard deviations when he mentions distribution factors. This alone tells us that probability distribution can't be flat. Another proof is that litz's tool gives approx. same results as mine. And mine is based on normal distributions.

Quote from: 375CT on June 27, 2014, 08:36:48 AM
I understand you are recomending going CEP for a more realistic simulation, am I right on my assumption?
No, I'm only recommending CEP for group size measuring. For wez tool you can use monte carlo or CEP depending which properties you value. I decided to go with CEP because for me it was more important to compare different calibers, bullets and conditions than get absolutely accurate results in hitting probability. Problem with monte carlo is that you get slightly different results for every calculation. That's not desirable if you try to compare something.

In practise you can never accurately calculate hitting probability anyway. That's simply because you don't know exact standard daviations for distribution factors. WEZ tool is always at it's best for comparing not for absolute probabilities.

Mman, thanks for the tips, they are much appreciated for sure.

#67
Ballistics / Re: Weapon Employment Zone
Last post by mman - June 27, 2014, 09:20:58 AM
Quote from: 375CT on June 27, 2014, 08:36:48 AM
Makes sense, but how to be sure? I get and agree to the point you made, but making no sense, well, that's the hard part out of this, because we are not dealing with any way to test the actual implementation.

Litz speaks about standard deviations when he mentions distribution factors. This alone tells us that probability distribution can't be flat. Another proof is that litz's tool gives approx. same results as mine. And mine is based on normal distributions.

Quote from: 375CT on June 27, 2014, 08:36:48 AM
I understand you are recomending going CEP for a more realistic simulation, am I right on my assumption?
No, I'm only recommending CEP for group size measuring. For wez tool you can use monte carlo or CEP depending which properties you value. I decided to go with CEP because for me it was more important to compare different calibers, bullets and conditions than get absolutely accurate results in hitting probability. Problem with monte carlo is that you get slightly different results for every calculation. That's not desirable if you try to compare something.

In practise you can never accurately calculate hitting probability anyway. That's simply because you don't know exact standard daviations for distribution factors. WEZ tool is always at it's best for comparing not for absolute probabilities.
#68
Ballistics / Re: Weapon Employment Zone
Last post by 375CT - June 27, 2014, 08:36:48 AM
Quote from: mman on June 27, 2014, 06:20:11 AM
Quote from: 375CT on June 26, 2014, 11:44:10 PM
Well, so far the original questions remains, is Litz's WEZ (a term taken from Air Combat for budget error analysis) flat or not? :-\ :-\
That's easy one. It must be normal distribution. No sense to use flat distribution, that would lead to strange results.

Makes sense, but how to be sure? I get and agree to the point you made, but making no sense, well, that's the hard part out of this, because we are not dealing with any way to test the actual implementation.

http://ballistipedia.com/index.php?title=Main_Page

Useful link for further discussion.

I understand you are recomending going CEP for a more realistic simulation, am I right on my assumption?
#69
Ballistics / Re: Weapon Employment Zone
Last post by mman - June 27, 2014, 06:20:11 AM
Quote from: 375CT on June 26, 2014, 11:44:10 PM
Well, so far the original questions remains, is Litz's WEZ (a term taken from Air Combat for budget error analysis) flat or not? :-\ :-\
That's easy one. It must be normal distribution. No sense to use flat distribution, that would lead to strange results.
#70
Ballistics / Re: Weapon Employment Zone
Last post by 375CT - June 26, 2014, 11:44:10 PM
Confirmed here

http://msdn.microsoft.com/en-us/library/2dx6wyd4(v=vs.110).aspx

Random in VB.net yields an uniform distribution...now, I need to figure out how bad this could be for creating something akin a WEZ run.

Anyway, like Robert pointed out, a RNG can be easily programmed if such need ever arises with for instance the Ziggurat algorithm.

Mman, thanks for the links, they just confirmed my suspicions on this too.

Now will also review CEP. Well, so far the original questions remains, is Litz's WEZ (a term taken from Air Combat for budget error analysis) flat or not? :-\ :-\