subdaily2daily: Sub-daily -> Daily

Description

Generic function for transforming a Sub-DAILY time series into a DAILY one

Usage

subdaily2daily(x, ...)
# S3 method for default
subdaily2daily(x, FUN, na.rm = TRUE, na.rm.max=0,
                       start="00:00:00", start.fmt= "%H:%M:%S", tz, ...)
# S3 method for zoo
subdaily2daily(x, FUN, na.rm = TRUE, na.rm.max=0,
                       start="00:00:00", start.fmt= "%H:%M:%S", tz, ...)
# S3 method for data.frame
subdaily2daily(x, FUN, na.rm = TRUE, na.rm.max=0,
           start="00:00:00", start.fmt= "%H:%M:%S", tz,
           dates=1, date.fmt="%Y-%m-%d %H:%M:%S", out.fmt="zoo", 
           verbose= TRUE, ...)
# S3 method for matrix
subdaily2daily(x, FUN, na.rm = TRUE, na.rm.max=0,
           start="00:00:00", start.fmt= "%H:%M:%S", tz,
           dates=1, date.fmt="%Y-%m-%d %H:%M:%S", out.fmt="zoo", 
           verbose= TRUE, ...)

Value

a zoo object with daily time series

Arguments

x

zoo, data.frame or matrix object, with sub-daily time series.
Measurements at several gauging stations can be stored in a data.frame or matrix object, and in that case, each column of x represents the time series measured in each gauging station, and the column names of x should correspond to the ID of each station (starting by a letter).

FUN

Function that have to be applied for aggregating from sub-daily into daily time step (e.g., for precipitation FUN=sum and for temperature and streamflows ts FUN=mean).

FUN MUST accept the na.rm argument, because na.rm is passed to FUN.

na.rm

Logical. Should missing values be removed?
-) TRUE : the daily values are computed only for days with a percentage of missing values less than na.rm.max
-) FALSE: if there is AT LEAST one NA within a day, the corresponing daily value in the output object will be NA.

na.rm.max

Numeric in [0, 1]. It is used to define the maximum percentage of missing values allowed in each day to keep the daily aggregated value in the output object of this function. In other words, if the percentage of missing values in a given day is larger or equal than na.rm.max the corresponding daily value will be NA.

start

character, indicating the starting time used for aggregating sub-daily time series into daily ones. It MUST be provided in the format specified by start.fmt.
This value is used to define the time when a new day begins (e.g., for some rain gauge stations).
-) All the values of x with a time attribute before start are considered as belonging to the day before the one indicated in the time attribute of those values.
-) All the values of x with a time attribute equal to start are considered to be equal to "00:00:00" in the output zoo object.
-) All the values of x with a time attribute after start are considered as belonging to the same day as the one indicated in the time attribute of those values.

It is useful when the daily values start at a time different from "00:00:00". Use with caution. See examples.

start.fmt

character indicating the format in which the time is provided in start, By default date.fmt=%H:%M:%S. See format in as.POSIXct.

tz

character, with the specification of the time zone used in both x and start. System-specific (see time zones), but "" is the current time zone, and "GMT" is UTC (Universal Time, Coordinated). See Sys.timezone and as.POSIXct.
If tz is missing (the default), it is automatically set to the time zone used in time(x).
This argument can be used to force using the local time zone or any other time zone instead of UTC as time zone.

dates

numeric, factor, POSIXct or POSIXt object indicating how to obtain the dates and times for each column of x (e.g., gauging station)
If dates is a number, it indicates the index of the column in x that stores the date and times
If dates is a factor, it is converted into POSIXct class, using the date format specified by date.fmt
If dates is already of POSIXct or POSIXt class, the code verifies that the number of elements on it be equal to the number of elements in x

date.fmt

character indicating the format in which the dates are stored in dates, By default date.fmt=%Y-%m-%d %H:%M:%S. See format in as.Date.
ONLY required when class(dates)=="factor" or class(dates)=="numeric".

out.fmt

OPTIONAL. Only used when x is a matrix or data.frame object /cr character, for selecting if the result will be a matrix/data.frame or a zoo object. Valid values are: numeric, zoo (default)

verbose

logical; if TRUE, progress messages are printed

...

arguments additional to na.rm passed to FUN.

Author

Mauricio Zambrano-Bigiarini, mzb.devel@gmail

Examples

Run this code

## Ex1: Computation of daily values, removing any missing value in 'x'

## Loading the time series of hourly streamflows for the station Karamea at Gorge
data(KarameaAtGorgeQts)
x <- KarameaAtGorgeQts

# Plotting the hourly streamflow values
plot(x)

# Subsetting 'x' to its first three days (01/Jan/1980 - 03/Jan/1980)
x <- window(x, end="1980-01-03 23:59:00")

## Transforming into NA the 10% of values in 'x'
set.seed(10) # for reproducible results
n           <- length(x)
n.nas       <- round(0.1*n, 0)
na.index    <- sample(1:n, n.nas)
x[na.index] <- NA

## Agreggating from Sub-Daily to Daily, removing any missing value in 'x'
( d1 <- subdaily2daily(x, FUN=mean, na.rm=TRUE) )


## Ex2: Computation of daily values, removing any missing value in 'x' and
##      considering that the new day starts at 08:00:00 local time
( d2 <- subdaily2daily(x, FUN=mean, na.rm=TRUE, start="08:00:00") )

## Ex3: Computation of daily values, removing any missing value in 'x' and
##      considering that the new day starts at 08:00:00, and forcing 
#       UTC both for 'x' and 'start'
( d3 <- subdaily2daily(x, FUN=mean, na.rm=TRUE, start="08:00:00", tz="UTC") )

######################
## Ex4: Compuation of daily values only when the percentage of NAs in each
#       day is lower than a user-defined percentage (10% in this example).
( d4 <- subdaily2daily(x, FUN=mean, na.rm=TRUE, na.rm.max=0.1) )