Variance Channel?

[richib2002]

Hi:
I want to create a maths channel showing the derivative of variance. Is variance available to use as a stand alone channel?

If not could this be added to the i2 wish list. It would be great to use this on say a track report

Cheers Rich

[DarrenR]

Hi Rich,

That is a good question. Variance is not a channel available to use in maths. It is not something that can be calculated correctly either as it is the delta of running lap time in a distance base, where all the custom maths is on a time base.
The best i think you can do is look at the difference in distance from the main to overlay and divide that by the current speed to see how much time difference there is for the distance. The error is introduced where there is a large difference in speed. Averaging the speeds from the main and overlay might help a little.
The maths is as follows -
('Corr Lap Dist' [m] - ref:'Corr Lap Dist' [m]) / (('Corr Speed' [m/s] + ref:'Corr Speed' [m/s]) /2)

putting 'ref:' in front of the channel name tells the maths to use the value of overlay 0. You can also use 'overlay:' which uses the value from overlay 1.

I'll put in the request to add variance to the channel list.

Cheers,

[Holmz]

Hi:
I want to create a maths channel showing the derivative of variance. Is variance available to use as a stand alone channel?

If not could this be added to the i2 wish list. It would be great to use this on say a track report

Cheers Rich

This is interesting.
What would you be computing the variance of?
And the derivative of?

You cold compute it as a custom maths function or .dll plug in...

[DarrenR]

The variance calc is the time difference at the same track distance from main to overlay. It's running lap/gain loss. taking the derivative of the variance shows time gain/loss per second. If you then use this channel for colour on a rainbow track map you can instantly see where you were faster and slower!

Yes a variance channel could be made with a custom function.

This is some of my data from the Winton fun day. The big variations are because of traffic but the two laps were a similar time. So you can see at the end of the old straight i was going more that 0.3sec/sec faster on one lap to the other, but on sweeper about the same amount slower.

[richib2002]

Hi Holmz:

As Darren has shown. if you could calculate the derivative of variance and display it on a rainbow map it would be an excellent way to quickly show a driver where he was faster and to what degree when comparing 2 laps.

Thanks darren I will try your calculation and see how it works

Rich

[Fermin]

Hello richib2002, I dont speak english, but if I understand you perhaps I can help you, I wait that you can understand me, my english is very bad.


The derivative of variance is actually:


(Speed Main Lap – Speed Overlay Lap) / Speed Main Lap


We can get this information, the first thing we have to do is prepare the Motec (only i2pro version 1.05).



Preparation Motec:



1) You create two constants:
“Main Lap” (Constant 1), with the value “-1” (for the moment).
“Overlay Lap” (Constant 2), with the value “-1” (for the moment).




2) You create the following mathematical formulas (VERY VERY VERY IMPORTANT, with the "B", "C1", "C2", "Change Here" and "Derivative of Variance" MUST TAKE THE RATE = 1000Hz AND DECIMAL = 3):



Speed Main Lap: 'Corr Speed' [km/h] * ((range_change("Outings:Laps") - 1) == 'Main Lap' [])


Speed Overlay Lap: 'Corr Speed' [km/h] * ((range_change("Outings:Laps") - 1) == 'Overlay Lap' [])


A: 1


B: integrate('A')


C1: stat_min(('B' * ('Speed Main Lap' > 0)) + (99999 * ('Speed Main Lap' == 0)))


C2: stat_min(('B' * ('Speed Overlay Lap' > 0)) + (99999 * ('Speed Overlay Lap' == 0)))


Change: 'C1' – 'C2'


Change Here: time_shift('Corr Speed' [km/h], 0.000)


Derivative of Variance: ('Corr Speed' [km/h] - 'Change Here') / 'Corr Speed' [km/h]





Now I'll explain to you how to use these formulas to instructions


Instructions:


1) Numeric gauge open a channel with "Change".

2) You open a Time / Distance Graph in the channel "Derivative of Variance".


3) You select the laps Main Lap and Overlay Lap.


4) You select the Main Lap in the top bar.


5) Edit the constants “Main Lap” and “Overlay Lap”, writing the number of the lap rightful. In my case, the “Main Lap” is 1 and the “Overlay Lap” is 2.


6) Edit the formula “Change Here” writing the number that the channel “Change” say, as you see in the image.


7) OK. You already have the channel "Derivative of Variance" operative. To change the laps repeating the instructions from step 3.


It is only an approximation. Regards