CST_QThreshold {CSIndicators} | R Documentation |
Transform an absolute threshold into probabilities
Description
From the user's perspective, an absolute threshold can be very useful for a
specific needs (e.g.: grape variety). However, this absolute threshold could
be transformed to a relative threshold in order to get its frequency in a given
dataset. Therefore, the function QThreshold
returns the probability of
an absolute threshold. This is done by computing the Cumulative Distribution
Function of a sample and leaving one out. The sample used will depend on the
dimensions of the data provided and the dimension names provided in sdate_dim
and memb_dim parameters:
Usage
CST_QThreshold(
data,
threshold,
start = NULL,
end = NULL,
time_dim = "time",
memb_dim = "member",
sdate_dim = "sdate",
ncores = NULL
)
Arguments
data |
An 's2dv_cube' object as provided function |
threshold |
An 's2dv_cube' object as output of a 'CST_' function in the same units as parameter 'data' and with the common dimensions of the element 'data' of the same length. A single scalar is also possible. |
start |
An optional parameter to defined the initial date of the period
to select from the data by providing a list of two elements: the initial
date of the period and the initial month of the period. By default it is set
to NULL and the indicator is computed using all the data provided in
|
end |
An optional parameter to defined the final date of the period to
select from the data by providing a list of two elements: the final day of
the period and the final month of the period. By default it is set to NULL
and the indicator is computed using all the data provided in |
time_dim |
A character string indicating the name of the temporal
dimension. By default, it is set to 'time'. More than one dimension name
matching the dimensions provided in the object |
memb_dim |
A character string indicating the name of the dimension in which the ensemble members are stored. |
sdate_dim |
A character string indicating the name of the dimension in which the initialization dates are stored. |
ncores |
An integer indicating the number of cores to use in parallel computation. |
Details
If a forecast (hindcast) has dimensions member and start date, and both must be used in the sample, their names should be passed in sdate_dim and memb_dim.
If a forecast (hindcast) has dimensions member and start date, and only start date must be used in the sample (the calculation is done in each separate member), memb_dim can be set to NULL.
If a reference (observations) has start date dimension, the sample used is the start date dimension.
If a reference (observations) doesn't have start date dimension, the sample used must be especified in sdate_dim parameter.
Value
An 's2dv_cube' object containing the probability of an absolute
threshold in the element data
.
Examples
threshold <- 26
exp <- NULL
exp$data <- array(abs(rnorm(112)*26), dim = c(member = 7, sdate = 8, time = 2))
class(exp) <- 's2dv_cube'
exp_probs <- CST_QThreshold(exp, threshold)
exp$data <- array(abs(rnorm(5 * 3 * 214 * 2)*50),
c(member = 5, sdate = 3, time = 214, lon = 2))
exp$attrs$Dates <- c(seq(as.Date("01-05-2000", format = "%d-%m-%Y"),
as.Date("30-11-2000", format = "%d-%m-%Y"), by = 'day'),
seq(as.Date("01-05-2001", format = "%d-%m-%Y"),
as.Date("30-11-2001", format = "%d-%m-%Y"), by = 'day'),
seq(as.Date("01-05-2002", format = "%d-%m-%Y"),
as.Date("30-11-2002", format = "%d-%m-%Y"), by = 'day'))
dim(exp$attrs$Dates) <- c(sdate = 3, time = 214)
class(exp) <- 's2dv_cube'
exp_probs <- CST_QThreshold(exp, threshold, start = list(21, 4),
end = list(21, 6))