[R] Assign name to object for each iteration in a loop.

[lglew]

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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