I have a data frame of vehicle trajectories. Here's a snapshot:
>dput(head(df))structure(list(vehicle = c(2L, 2L, 2L, 2L, 2L, 2L), frame =
>43:48, globalx = c(6451214.156, 6451216.824, 6451219.616, 6451222.548,
>6451225.462, 6451228.376), class = c(2L, 2L, 2L, 2L, 2L, 2L), velocity =
>c(37.76, 37.9, 38.05, 38.18, 38.32, 38.44 ), lane = c(2L, 2L, 2L, 2L, 2L,
>2L)), .Names = c("vehicle", "frame", "globalx", "class", "velocity", "lane"),
>row.names = c(NA, 6L), class = "data.frame")
where, vehicle= vehicle id, frame= frame id of time frames in which it was
observed, globalx = x coordinate of the front center of the vehicle, class=type
of vehicle (1=motorcycle, 2=car, 3=truck), velocity=speed of vehicles in feet
per second, lane= lane number (there are 6 lanes).The 'frame' represents one
tenth of a second i.e. one frame is 0.1 seconds long. At frame 't' the vehicle
has globalx coordinate x(t) and at frame 't-1' (0.1 seconds before) it was
x(t-1). If the reference location has globalx coordinate=6451179.1116 then I
simply want a new column in df called 'u' which has 'yes' in the row where
globalx of the vehicle was greater than reference coordinate at 'U' AND the
previous consecutive globalx coordinate of this vehicle was less than reference
coordinate at 'U'(i.e. reference coordinate is between the 2 locations of
vehicle in two consecutive frames). This means that if df has 100 vehicles then
there will be 100 'yes' in 'u' column because every vehicle wil!
l meet the above criteria only once. I have tried to do this by running the
function with ifelse and also tried to do the same using a for loop but it
doesn't work for me.
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