Assign name to object for each iteration in a loop.

Hi R-users,

I'm trying to produce decompositions of a multiple time-series, grouped by a
factor (called "area"). I'm modifying the code in the STLperArea function of
package ndvits, as this function only plots produces stl plots, it does not
return the underlying data.

I want to extract the trend component of each decomposition
("x$time.series[,trend]), assign a name based on the factor "area".

My input data look like this:
Area is a factor, with three (but could be many more) levels.
area
1
2
3

Ystart=2000

TS is a timeseries:

?X2000049 ? X2000065 ?X2000081 ?X2000097 ?X2000113
1 ? ? 0.2080 ? ? ?0.2165 ? ? ?0.2149 ? ? 0.2314 ? ? ?0.2028
2 ? ? 0.1578 ? ? ?0.1671 ? ? ?0.1577 ? ? 0.1593 ? ? ?0.1672
3 ? ? 0.1897 ? ? ?0.1948 ? ? ?0.2290 ? ? 0.2292 ? ? ?0.2067

Here's the function:

STLpA<-function(TS, area, Ystart, period=23, nSG="5,5", DSG=0)
{
require (RTisean)
for(i in 1:unique(area)){
vi.metric=TS[area==i]
filt.vi<-sav_gol(vi.metric,n=nSG,D=DSG)
vi.sg<-ts(filt.vi[,1], start=Ystart,frequency=period)
stld.tmp<-stl(vi.sg, s.window="periodic", robust=TRUE, na.action=na.approx)
stld.trend<-stld.temp$time.series[,trend]
}
assign(paste("stld", i , sep= "."), stld.trend)
vi.trend<-ls(pattern= "^stld..$")
return(vi.trend)
}

When I call this function with signal=STLpA(TS,area,Ystart=2000,period=23,
nSG= "5,5", DSG="0"))

I get this error:

Error in cat(list(...), file, sep, fill, labels, append) :
?argument 1 (type 'list') cannot be handled by 'cat'
In addition: Warning message:
In 1:unique(area) :
?numerical expression has 3 elements: only the first used

I'm guessing this is because I'm assigning names to each temporary stl.trend
file incorrectly. Can anyone
improve on my rather poor efforts here?

Many thanks,

Louise




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