I've tried to make the description more clear in the wiki. regards, Jakob 2018-03-07 12:37 GMT+01:00 eegea <ee...@protonmail.com>:

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> Hello Jakob, > thanks a lot, now it is more clear. > The problem is that I was assuming that sampledSecond is just the number > of seconds there were vehicles on the lane, not the sum of the number of > seconds of every vehicle on the lane. I was assuming that if your measure > interval is, say 10 s, then sampledSeconds<=10 always. Even though it is > on the wiki, I think it is not clear enough. > > Best regards, > Esteban > > > Sent with ProtonMail <https://protonmail.com> Secure Email. > > ‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐ > On 7 March 2018 10:10 AM, Jakob Erdmann <namdre.s...@googlemail.com> > wrote: > > Hello, > I admit the formula is a bit hard to read. > > Consider an aggregation period of 1s. In that case each vehicle on the > lane results in 1 sampled second so sampleSeconds gives the number of > vehicles on the lane. > Since the length of the lane is in m we get the density #veh/m by dividing > by myLaneLength. > To get #veh/km we multiply by 1000 > > For longer periods, if the number of vehicle on the lane stays constant, > it should be obvious that the sampleSeconds is a multiple of the number and > the period and the formula is correct as well. > > If the number of vehicles changes during the aggregation period, the > formula gives the appropriate average. > regards, > Jakob > > 2018-03-06 18:59 GMT+01:00 eegea <ee...@protonmail.com>: > >> According to the wiki (http://sumo.dlr.de/wiki/Simul >> ation/Output/Lane-_or_Edge-based_Traffic_Measures) >> density is given as "#veh/km" >> However, looking at the source in MSMeanData_Net line 179 and 208 it is >> computed as >> >> >> dev.writeAttr("density", sampleSeconds / STEPS2TIME(period) * (SUMOReal) >> 1000 / myLaneLength) >> >> I cannot see why the above gives the number of vehicles per Km in the >> lane during the period. As far as I see, sampleSeconds is updated as >> expected >> sampleSeconds += timeOnLane >> so it seems to be what the wiki says "Number seconds vehicles were >> measured on the edge/lane". >> It seems that we have the fraction of time the lane has been occupied >> multiplied by 1000 and divided by the lane length. >> Is this an error or is this coming from some formula I do not know of? >> >> _______________________________________________ >> sumo-user mailing list >> sumo-user@eclipse.org >> To change your delivery options, retrieve your password, or unsubscribe >> from this list, visit >> https://dev.eclipse.org/mailman/listinfo/sumo-user >> >> >

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