blocks-class {covatest}

Class "blocks"

Description

A class for overlapped blocks of the time series associated with the given spatial points specified through the function couples. Thus, it is necessary to execute couples first and then blocks

Usage

blocks(lb, ls, matdata, pardata1, pardata2, stpairs)

## S4 method for signature 'blocks'
boxplot(x, i, j, ...)

## S4 method for signature 'blocks'
show(object)

## S4 method for signature 'blocks'
x[i, j, drop = FALSE]

## S4 method for signature 'blocks'
summary(object, i, j)

Arguments

lb

integer, length of each block. The number of terms in each block must be greater than 5 and smaller than the quarter part of the length of each time series

ls

integer, number of overlapped data between two consecutive blocks. The number of overlapped terms between two consecutive blocks must in the interval [0, lb/2]

matdata

STFDF/STSDF or data.frame, which contains the coordinates of the spatial points, the identification code of the spatial points, the indentification code of the temporal points and the values of the variable, typically output from read.STdata

pardata1

integer, it represents the column in which the spatial ID is stored (if the spatio-temporal data set is given as data.frame) or the number of variables in the STFDF/STSDF (if the data are given as a STFDF/STSDF)

pardata2

integer, it represents the column in which the values of the variable are stored (if the spatio-temporal data set is given as data.frame) or the slot in which the values of the variable of interest are stored (if the data are given as a STFDF/STSDF). Note that for STFDF/STSDF the argument is set, by default, equal to 1 if the number of variables is equal to 1

stpairs

object of class couples, containing the spatial points and the corresponding temporal lags to be analyzed

x

object of class blocks for methods boxplot and extract

i

index specifying the block to be selected. If i=0 all blocks are selected automatically (option available only for boxplot and summary methods)

j

index specifying the spatial point to be selected. If j=0 all spatial points are selected automatically (option available only for boxplot and summary methods)

...

any arguments that will be passed to the panel plotting functions

object

object of class blocks for methods show and summary

drop

logical, the argument is set, by default, equal to FALSE to preserve the structure of the object. It is advisable not to change this option

Details

A message informs the user of the number of blocks extracted

Slots

mat.block

matrix of dimension (lb x overall number of blocks); the columns of this matrix are associated with the different blocks, of length equal to lb, that can be extracted from the time series related to the selected spatial points defined in the slot stpairs of couples, identified as [e-mail]

array.block

array of dimension (lb x number of blocks for each selected spatial points x number of spatial points). In each table of this array, the overlapped blocks for each spatial location are available

sel.staz

numeric or character; contains the ID codes of the selected spatial points

Note

• "Error in matdata[, clvr]: subscript out of bounds" appears if pardata2 does not exist in the argument matdata

• If "Error in matdata[, clvr]" appears, no data for some of the spatial points, specified in stpairs, are available. The user has to go back to couples and revise the vector of the selected spatial points (sel.staz and sp.couples.in arguments)

• A stop occurs if more than 75% of consecutive data are missing in the time series, since a large number of missing values do not guarantee the reliability of the tests

• A stop occurs if the length of the time series for each spatial points is less than 29

• A message appears if the length of the time series for each spatial point is greater than 29 and less than 89, since the length of the time series is low and may not guarantee the reliability of the tests

• A stop occurs if more than 80% of consecutive data are missing in one of the blocks, since the estimation of the covariance matrix is not reliable, when a large number of missing values occur

• If, in the last block of each selected spatial point, more than 15% of data are missing a warning message appears, since the estimation of the covariance matrix, when a large number of missing values occurs, is not reliable

• A warning message appears if the number of blocks, computed by fixing lb and ls, is less than 5. It is convenient that the number of blocks is close to the number of spatio-temporal comparisons defined in couples. This avoids singolarity in computing test statistics

References

Cappello, C., De Iaco, S., Posa, D., 2018, Testing the type of non-separability and some classes of space-time covariance function models. Stochastic Environmental Research and Risk Assessment, 32 17–35

Cappello, C., De Iaco, S., Posa, D., 2020, covatest: An R Package for Selecting a Class of Space-Time Covariance Functions. Journal of Statistical Software, 94(1) 1–42.

De Iaco, S., Palma, M., Posa, D., 2016. A general procedure for selecting a class of fully symmetric space-time covariance functions. Environmentrics, 27(4) 212–224.

Li, B., Genton, M.G., Sherman, M., 2007, A nonparametric assessment of properties of spacetime covariance functions. Journal of the American Statistical Association, 102 736–744.

See Also

couples

read.STdata

Examples

# --start define the STFDF rr_13-- #
library(sp)
library(spacetime)
#library(gstat)
data(air)
ls()
if (!exists("rural")) rural = STFDF(stations, dates, data.frame(PM10 =
as.vector(air)))
rr = rural[,"2005::2010"]
unsel = which(apply(as(rr, "xts"), 2, function(x) all(is.na(x))))
r5to10 = rr[-unsel,]
rr_13 <- r5to10[c("DEHE046","DESN049","DETH026","DENW063","DETH061","DEBY047",
"DENW065","DEUB029","DENW068","DENI019","DEHE051","DERP016","DENI051"),
"2005::2006"]
# --end define the STFDF rr_13-- #


sel.staz.sym <- c("DERP016", "DENW065", "DEHE051", "DETH026", "DENW063", "DENI019",
"DENW068", "DEHE046", "DEUB029", "DEBY047", "DETH061", "DESN049")

sp.couples.in.sym <- matrix(data = c("DERP016", "DENW065", "DEHE051", "DETH026",
"DENW063", "DENI019", "DENW068", "DEHE046", "DEUB029", "DEBY047", "DETH061", "DESN049"),
ncol = 2, byrow = TRUE)

t.couples.in.sym <- c(1, 2)

couples.sym <- couples(sel.staz = sel.staz.sym, sp.couples.in = sp.couples.in.sym,
t.couples.in = t.couples.in.sym, typetest = "sym", typecode = character())

block.sym <- blocks(lb = 40, ls = 10, matdata = rr_13, pardata1 = 1, pardata2 = 1,
stpairs = couples.sym)

### methods for blocks
#1. show
block.sym

#2. [  extract
block.sym[1,] #select the 1st block of each spatial location
block.sym[,1] #select all blocks of the 1st spatial location
block.sym[1:2, 1:3] #select the first two blocks of the first 3 spatial locations

#3. summary
summary(block.sym, 1:2, 1:3) #to obtain the summary associated to the first
#two blocks of the first 3 spatial locations

summary(block.sym, 0, 1) #to obtain the summary associated to all blocks of
#the 1st spatial location

#4. boxplot
boxplot(block.sym, 1:5, 1:2) #boxplots of the first 5 blocks of associated to
#the first 2 spatial locations

boxplot(block.sym, 0 ,1) #boxplots of all blocks of associated to the 1st
#spatial location