hydroTSM (version 0.2-0)

seasonalfunction: Seasonal Function

Description

Generic function for applying any R function to a zoo object, in order to obtain 4 representative seasonal values.

Usage

seasonalfunction(x, ...)
## S3 method for class 'default':
seasonalfunction(x, FUN, na.rm = TRUE, ...)
## S3 method for class 'data.frame':
seasonalfunction(x, FUN, na.rm = TRUE, dates, date.fmt = "\%Y-\%m-\%d", 
                          out.type = "data.frame", verbose = TRUE, ...)

Arguments

x

zoo, data.frame or matrix object, with daily or monthly time series. Measurements at several gauging stations can be stored in a data.frame of matrix object, and in that case, each column of x represent the time series measured in each gaugi

FUN

Function that will be applied to ALL the values in x belonging to each one of the 4 weather seasons (e.g., FUN can be some of mean, max, min, sd). The FUN value for the wint

na.rm

Logical. Should missing values be removed before the computations? -) TRUE : the monthly values are computed considering only those values in x different from NA (very important when FUN=sum) -) FALSE

dates

numeric, factor, Date indicating how to obtain the dates. If dates is a number, it indicates the index of the column in x that stores the dates If dates is a factor, it is converted into Date class, by using the da

date.fmt

Character indicating the format in which the dates are stored in dates, e.g. %Y-%m-%d. See format in format.Date. ONLY required when class(dates)=="factor

out.type

Character defining the desired type of output. Valid values are: -) data.frame: a data.frame, with 4 columns representing the weather seasons, and as many rows as stations are included in x -) db : a data.frame,

verbose

Logical; if TRUE, progress messages are printed

...

further arguments passed to or from other methods

Warning

The FUN value for the winter season (DJF) is computed considering the consecutive months of December, January and February. Therefore, if x starts in January and ends in December of any year, the winter value of the first year is computed considering only the January and February value of that year, whereas the December value of the first year is used to compute the winter value of the next year.

See Also

dm2seasonal, monthlyfunction, annualfunction, extractzoo

Examples

## Loading the SanMartino precipitation data
data(SanMartinoPPts)
x <- SanMartinoPPts

## Daily to Annual
a <- daily2annual(x, FUN=sum, na.rm=TRUE)

# Amount of years
nyears <- length(seq(from=as.Date("1921-01-01"), to=as.Date("1990-12-31"), by="years"))

## Mean annual precipitation.
# It is necessary to divide by the amount of years to obtain the mean  annual value, 
# otherwise it will give the total precipitation for all the 70 years
seasonalfunction(x, FUN=sum, na.rm=TRUE) / nyears

#####################
### verification ####
# Mean winter (DJF) value
sum( extractzoo(x, trgt="DJF") ) / nyears

# Mean spring (MAM) value
sum( extractzoo(x, trgt="MAM") ) / nyears

# Mean summer (JJA) value
sum( extractzoo(x, trgt="JJA") ) / nyears

# Mean autumn (SON) value
sum( extractzoo(x, trgt="SON") ) / nyears