filter_vpts: Filter a time series of vertical profiles ('vpts').

Description

Filter a time series of vertical profiles ('vpts') by a start and end time, for night or day time, or extract profile nearest to provided timestamp. Use argument night = TRUE to select only time stamps between sunset and sunrise, or night = FALSE to select daytime (sunrise to sunset). Selection for night and day uses check_night().

Usage

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

Value

A vpts object, or a vp object when nearest is specified.

Arguments

x: A vpts object.
min: POSIXct date or character. Minimum datetime to be included.
max: POSIXct date or character. Datetime up to this maximum included.
nearest: POSIXct date or character. If specified, min and max are ignored and the profile (vp) nearest to the specified datetime is returned that matches the day/night selection criteria.
night: When TRUE selects only nighttime profiles, when FALSE selects only daytime profiles, as classified by check_night().
elev: Numeric (vector). Sun elevation in degrees defining nighttime. May also be a numeric vector of length two, with first element giving sunset elevation, and second element sunrise elevation.
offset: Numeric (vector). Time duration in seconds by which to shift the start and end of nighttime. 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.

Details

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

Examples

Run this code

# Select profiles later than 02 Sep 2016

# Select the profile nearest to 2016-09-01 03:00 UTC
filter_vpts(example_vpts, nearest = "2016-09-01 03:00")

# Select profiles between than 01:00 and 03:00 UTC on 02 Sep 2016
filter_vpts(example_vpts, min = "2016-09-02 01:00", max = "2016-09-02 03:00")

# Select daytime profiles (i.e. profiles between sunrise and sunset)
filter_vpts(example_vpts, night = FALSE)

# Select nighttime profiles, with nights starting and ending at
# civil twilight (when the sun is 6 degrees below the horizon)
filter_vpts(example_vpts, night = TRUE, elev = -6)

# Select nighttime profiles from 3h after sunset to 2h before sunrise
filter_vpts(example_vpts, night = TRUE, offset = c(3, -2)*3600)