Time and night/day selection in a time series of vertical profiles ('vpts')

filter_vpts(x, min, max, nearest, night, elev = -0.268, offset = 0)

Arguments

x: A vpts object.
min: Minimum datetime to be included. POSIXct value or character string convertible to POSIXct.
max: Maximum datetime to be included. POSIXct value or character string convertible to POSIXct.
nearest: If specified, min and max are ignored and the profile nearest to the specified datetime is returned that matches the day/night selection criteria. POSIXct value or character string convertible to POSIXct.
night: When TRUE select only night time profiles, when FALSE select only day time profiles, as classified by check_night.
elev: numeric. Sun elevation in degrees defining night time. May also be a numeric vector of length two, with first element giving sunset elevation, and second element sunrise elevation.
offset: numeric. Time duration in seconds by which to shift the start and end of night time. May also be a numeric vector of length two, with first element added to moment of sunset and second element added to moment of sunrise. See check_night for details.

Value

An object of class 'vpts', or an object of class 'vp' if argument nearest is specified.

Details

Returns profiles for which min <= timestamp profile < max. Selection for night and day occurs by check_night.

Examples

# load example vertical profile time series:
data(example_vpts)
example_vpts
#>                    Irregular time series of vertical profiles (class vpts)
#> 
#>            radar:  KBGM 
#>       # profiles:  1934 
#> time range (UTC):  2016-09-01 00:02:00 - 2016-09-10 11:56:00 
#>    time step (s):  min: 180     max:  16320 

# select profiles later than 02-Sep-2016
filter_vpts(example_vpts, min = "2016-09-02")
#>                    Irregular time series of vertical profiles (class vpts)
#> 
#>            radar:  KBGM 
#>       # profiles:  1651 
#> time range (UTC):  2016-09-02 00:06:00 - 2016-09-10 11:56:00 
#>    time step (s):  min: 180     max:  16320 

# select the profile nearest to 2016-09-01 03:00 UTC:
filter_vpts(example_vpts, nearest = "2016-09-01 03:00")
#>                Vertical profile (class vp)
#> 
#>        radar:  KBGM 
#>       source:  
#> nominal time:  2016-09-01 03:02:00 
#> generated by:   

# select profiles between than 1 and 3 UTC on 02-Sep-2016:
filter_vpts(example_vpts, min = "2016-09-02 01:00", max = "2016-09-02 03:00")
#>                    Irregular time series of vertical profiles (class vpts)
#> 
#>            radar:  KBGM 
#>       # profiles:  13 
#> time range (UTC):  2016-09-02 01:04:00 - 2016-09-02 02:59:00 
#>    time step (s):  min: 540     max:  600 

# select day time profiles (day time periods from sunrise to sunset)
filter_vpts(example_vpts, night=FALSE)
#>                    Irregular time series of vertical profiles (class vpts)
#> 
#>            radar:  KBGM 
#>       # profiles:  910 
#> time range (UTC):  2016-09-01 10:35:00 - 2016-09-10 11:56:00 
#>    time step (s):  min: 180     max:  41460 

# select night time profiles, with nights starting starting and ending at civil twilight
# (when the sun is 6 degrees below the horizon):
filter_vpts(example_vpts, night=TRUE, elev = -6)
#>                    Irregular time series of vertical profiles (class vpts)
#> 
#>            radar:  KBGM 
#>       # profiles:  938 
#> time range (UTC):  2016-09-01 00:10:00 - 2016-09-10 10:10:00 
#>    time step (s):  min: 180     max:  55200 

# select night time profiles from 3 hours after sunset to 2 hours before sunrise
filter_vpts(example_vpts, night=TRUE, offset=c(3,-2)*3600)
#>                    Irregular time series of vertical profiles (class vpts)
#> 
#>            radar:  KBGM 
#>       # profiles:  578 
#> time range (UTC):  2016-09-01 02:39:00 - 2016-09-10 08:41:00 
#>    time step (s):  min: 180     max:  65460