openair functions usually through the option
type.cutData(x, type = "default", hemisphere = "northern",
n.levels = 4, is.axis = FALSE, ...)
cutDaylight(x, local.hour.offset = 0, latitude =
51.522393, longitude = -0.154700, ...)date.type ca"northern" or
"southern", used to split data into seasons.TRUE/FALSE), used
to request shortened cut labels for axes.cutDaylight to estimate if the measurement
was collected during daylight or nighttime hours.
local.hour.offset gives the measurement timezone
and latitude and longitude givcond that is
defined by type.typetype. Note that all time
dependent types require a column date.
"default" does not split the data but will describe the
levels as a date range in the format "day month year".
"year" splits the data by each year.
"month" splits the data by month of the year.
"hour" splits the data by hour of the day.
"monthyear" splits the data by year and month. It differs
from month in that a level is defined for each month of
the data set. This is useful sometimes to show an ordered
sequence of months if the data set starts half way
through a year; rather than starting in January.
"weekend" splits the data by weekday and weekend.
"weekday" splits the data by day of the week - ordered to
start Monday.
"season" splits data up by season. In the northern
hemisphere winter = December, January, February; spring =
March, April, May etc. These defintions will change of
hemisphere = "southern".
"daylight" splits the data relative to estimated sunrise
and sunset to give either daylight or nighttime. The cut
is made by cutDaylight but more conveniently
accessed via cutData, e.g. cutData(mydata,
type = "daylight", latitude=my.latitude,
longitude=my.longitude). The daylight estimation, which
is valid for dates between 1901 and 2099, is made using
the measurement location, date, time and astronomical
algorithms to estimate the relative positions of the Sun
and the measurement location on the Earth's surface, and
is based on NOAA methods
(local.hour.offset is zero if you are working in
UTC/GMT, otherwise see
latitude (+ to North; - to
South) and longitude (+ to East; - to West).
"gmtbst" or "bstgmt" will split the data by hours that
are in GMT i.e. mostly winter months) and hours in
British summertime. Each of the two periods will be in
local time. The main purpose of this option is to
test whether there is a shift in the diurnal profile when
GMT and BST hours are compared. This option is
particularly useful with the timeVariation
function. For example, close to the source of road
vehicle emissions, `rush-hour' will tend to occur at the
same local time throughout the year e.g. 8 am and
5 pm. Therefore, comparing GMT hours with BST hours will
tend to show similar diurnal patterns (at least in the
timing of the peaks, if not magnitude) when expressed in
local time. By contrast a variable such as wind speed or
temperature should show a clear shift when expressed in
local time for BST vs. GMT. In essence, this option when
used with timeVariation may help determine whether
the variation in a pollutant is driven by man-made
emissions or natural processes.
"wd" splits the data by 8 wind sectors and requires a
column wd: "NE", "E", "SE", "S", "SW", "W", "NW",
"N".
"ws" splits the data by 8 quantiles of wind speed and
requires a column ws.
"site" splits the data by site and therefore requires a
column site.## split data by day of the week
mydata <- cutData(mydata, type = "weekday")Run the code above in your browser using DataLab