Help Understanding Charts

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FEJICU
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Help Understanding Charts

Post by FEJICU »

Hi,

First of all let me say that I find this app amazing and mostly easy to use.

Yesterday I went to my local track (which I intend to try and certify in the future) and recorded a couple of laps. On the second run the app crashed after two recorded laps and later reported an error in the database. I was able nonetheless to get everything working again afterwards.

My question is regarding the Speed Chart attached. As you seen the red line (reference) shows a faster top speed on the main straight, but the time gap shows a negative time difference (meaning the reference lap was at that point slower than the other lap). Afterwards time is made up achieving the fastest lap. But what I don't understand is how given a faster speed on a straight can the time gap chart show a negative time gap?

Please see the attached image.

Thank you
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Harry
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Re: Help Understanding Charts

Post by Harry »

Overall, the reference lap (red) has been faster than the selected lap (gray). This can be seen from the final blue value which is around + 1 second. In the beginning, the selected lap has been better than the reference lap. This is due to the fact the gray line is faster in most places than the red one. So peak speed has been higher on the reference lap, but this speed has not been kept on the following straight. For the time to the first peak speed, the blue area should probably be above zero... The reason for this needs to be analyzed in detail. I guess this is the result of in-accuracy of speed recorded vs. distance made good. The blue area is calculated by comparing positions on track (lots of interpolation) only, it is not derived from speeds recorded at all.

- Harry

P.S. For your crashes, please send the log files to my email address. Here is a good 'how to'.
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FEJICU
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Re: Help Understanding Charts

Post by FEJICU »

Actually the phone didn't crash, just the app. It stopped working and the phone went to its home screen.
hms
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Re: Help Understanding Charts

Post by hms »

Harry,
The blue area is calculated by comparing positions on track (lots of interpolation) only, it is not derived from speeds recorded
What does the blue area actually represent?
Is it the difference in time between reference and actual lap, using the blue scale on the right (1 second?)
I have worked this out now. It's a bar chart where the bars are stacked next to each other, the area under the curve means nothing! Each bar represents the difference in time against the reference lap, for that position on the track on the reference lap. Scale on the right hand vertical axis, in seconds.
If below the horizontal x axis then you are ahead of the reference lap, if above the horizontal x axis then you are behind the reference lap.
H
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Harry
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Re: Help Understanding Charts

Post by Harry »

In a mathematical sense, the area under the blue plot makes no sense and should be a line like the red and the gray ones - you are right. On the other hand, the y value of the blue plot is a value derived from aggregated losses and gains in time... As areas are perceived as aggregated values, this means the display as an area is probably acceptable despite the mathematical correct interpretation?

- Harry
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Harry
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Re: Help Understanding Charts

Post by Harry »

FEJICU wrote:Actually the phone didn't crash, just the app. It stopped working and the phone went to its home screen.
That's clear, iPhone never crash :D My point on crash logs was exactly on application crash logs. So if you can extract these, that would be helpful.

- Harry
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hms
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Re: Help Understanding Charts

Post by hms »

Harry wrote:In a mathematical sense, the area under the blue plot makes no sense and should be a line like the red and the gray ones - you are right. On the other hand, the y value of the blue plot is a value derived from aggregated losses and gains in time... As areas are perceived as aggregated values, this means the display as an area is probably acceptable despite the mathematical correct interpretation?

- Harry
The issue is just knowing what it means. Once you know that it's OK.

h
Black S Special goes by the name of Lexie.
JRSC M45, 189.6 bhp JR ARB's, TDR belt tensioner, Steve Heath Rose jointed drop links, Absolutely Shocks GAZ springs and dampers, Alignment by WIM

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