[R-sig-Geo] Order raster images in a levelplot

[Frede Aakmann Tøgersen]

Hi

Since no code example was provided we'll have to guess. I suppose it has to do with the way factor() works.

Here is the built-in list of month names in R:

> month.name
 [1] "January"   "February"  "March"     "April"     "May"       "June"     
 [7] "July"      "August"    "September" "October"   "November"  "December" 

Now show this as a factor:

> factor(month.name)
[1] January   February  March     April     May       June      July     
 [8] August    September October   November  December 
12 Levels: April August December February January July June March ... September

See how factor() is using lexicographical order for the labels of the factor levels.

Now do this  instead:

> factor(month.name, labels = month.name)
[1] May       April     August    January   September July      June     
 [8] February  December  November  October   March    
12 Levels: January February March April May June July August ... December

Now the order of the labels of the levels is the same as that of month.name.

Here is an example:

testdata <- data.frame(x = 1, y = 1, Month = factor(month.name))

### order of panels is that of order(month.name)
xyplot(y ~ x|Month, data = testdata)

testdata <- data.frame(x = 1, y = 1, Month = factor(month.name, labels = month.name))

### order of panels is that of month.name
### January in bottom left and Deccember in top right panel
xyplot(y ~ x|Month, data = testdata)

### use the as.table argument to get January in top left and December in bottom right
xyplot(y ~ x|Month, data = testdata, as.table = TRUE)


Yours sincerely / Med venlig hilsen


Frede Aakmann Tøgersen
Specialist, M.Sc., Ph.D.
Plant Performance & Modeling

Technology & Service Solutions
T +45 9730 5135
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> -----Original Message-----
> From: r-sig-geo-bounces at r-project.org [mailto:r-sig-geo-bounces at r-
> project.org] On Behalf Of Oscar Perpiñán Lamigueiro
> Sent: 21. oktober 2014 07:50
> To: Navinder Singh
> Cc: r-sig-geo at r-project.org
> Subject: Re: [R-sig-Geo] Order raster images in a levelplot
> 
> Hi,
> 
> > 1. Does someone have any suggestions on how i can order the sequence
> > of images in a “levelplot" made using rasterVis.  Specifically, i
> > have months i need to arrange in the normal sequence, as the plot
> > currently aligns them in an alphabetical order. Does “levelplot”
> > works the same way as xyplots in lattice?
> 
> levelplot methods defined in rasterVis are based on lattice graphics.
> Most of the arguments provided by lattice::xyplot and
> lattice::levelplot are also available. For this issue you could try
> these arguments: perm.cond, index.cond, as.table. All of them are
> described in the help page of lattice::xyplot.
> 
> > 2. Have there been more developments on the zApply function in the
> > raster package? I am trying to make basic statistical summaries for
> > mean monthly (eg. NDVI values) form a multi annual time series.  How
> > does one go about using the “by" Indexing in this case.
> 
> Could you post a reproducible example? I have used zApply for similar
> tasks without problems.
> 
> Best,
> 
> Oscar.
> 
> --
> Oscar Perpiñán Lamigueiro
> Dpto. Ingeniería Eléctrica (ETSIDI-UPM)
> Grupo de Sistemas Fotovoltaicos (IES-UPM)
> URL: http://oscarperpinan.github.io
> 
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