hi all
I have this dataframe (created as a reproducible example)
mydf<-structure(list(date_time = structure(c(1508238000, 1508238000,
1508238000, 1508238000, 1508238000, 1508238000, 1508238000), class =
c("POSIXct", "POSIXt"), tzone = ""),
direction = structure(c(1L, 1L, 1L, 1L, 2L, 2L, 2L), .Label = c("A", "B"),
class = "factor"),
type = structure(c(1L, 2L, 3L, 4L, 1L, 2L, 3L), .Label = c("car", "light_duty",
"heavy_duty", "motorcycle"), class = "factor"),
avg_speed = c(41.1029082774049, 40.3333333333333, 40.3157894736842,
36.0869565217391, 33.4065155807365, 37.6222222222222, 35.5),
n_vehicles = c(447L, 24L, 19L, 23L, 706L, 45L, 26L)),
.Names = c("date_time", "direction", "type", "speed", "n_vehicles"),
row.names = c(NA, -7L),
class = "data.frame")
mydf
and I need to get to this final result
mydf_final<-structure(list(date_time = structure(c(1508238000, 1508238000,
1508238000, 1508238000), class = c("POSIXct", "POSIXt"), tzone = ""),
type = structure(c(1L, 2L, 3L, 4L), .Label = c("car", "light_duty",
"heavy_duty", "motorcycle"), class = "factor"),
weighted_avg_speed = c(36.39029, 38.56521, 37.53333, 36.08696),
n_vehicles = c(1153L,69L,45L,23L)),
.Names = c("date_time", "type", "weighted_avg_speed", "n_vehicles"),
row.names = c(NA, -4L),
class = "data.frame")
mydf_final
my question:
how to compute a weighted mean i.e. "weighted_avg_speed"
from "speed" (the values whose weighted mean is to be computed) and
"n_vehicles" (the weights)
grouped by "date_time" and "type"?
to be noted the complication of the case "motorcycle" (not present in both
directions)
any help for that?
thank you
max
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