[STATSGRASS] spatstat: trend to spatialgriddataframe - help needed

[Roger Bivand]

On Thu, 10 May 2007, Jarekj Jasiewicz wrote:

> Hi
> 
> It seems very simple but I cannot pass throuh one step:
> 
> I computed trend (ppm) in spatstat package:
> 
>     ppm_2=ppm(unmark(pp), ~polynom(x,y,2))
> 
> next I found, that I can convert that  object to  "something almost 
> like  <<im>> object" :
> 
>     k=plot(ppm_2, ngrid=c(gmeta6()$cols, gmeta6()$rows), 
> superimpose=FALSE, how="image", pause=FALSE, plot.it=FALSE)
> 
> but: it is not im object. It is object which only contains im inside. 
> Here is its structure:
> 
> str(k)
> List of 1
>  $ trend:List of 1
>   ..$ :List of 11     ##here is something like "unnamed atribute" I 
> cannot pass this

Try str(k$trend[[1]]$v) - if this accesses the matrix with the [[ operator
(first unnamed component of trend), then the other bits ought to follow.
Please note that polynom() does not protect the powered coordinates from
numerical overflow, so I'd be cautious unless you know that x and y are
only small numbers.

Roger

>   .. ..$ v     : num [1:986, 1:1051] 1.06e-09 1.07e-09 1.08e-09 1.10e-09 
> 1.11e-09 ...
>   .. ..$ dim   : int [1:2] 986 1051
>   .. ..$ xrange: num [1:2] 3684409 3713995
>   .. ..$ yrange: num [1:2] 5649780 5681325
>   .. ..$ xstep : num 28.2
>   .. ..$ ystep : num 32
>   .. ..$ xcol  : num [1:1051] 3684423 3684451 3684479 3684507 3684535 ...
>   .. ..$ yrow  : num [1:986] 5649796 5649828 5649860 5649892 5649924 ...
>   .. ..$ lev   : NULL
>   .. ..$ type  : chr "real"
>   .. ..$ units :List of 3
>   .. .. ..$ singular  : chr "unit"
>   .. .. ..$ plural    : chr "units"
>   .. .. ..$ multiplier: num 1
>   .. .. ..- attr(*, "class")= chr "units"
>   .. ..- attr(*, "class")= chr "im"
>  - attr(*, "class")= chr "plotppm"
>  - attr(*, "mrkvals")= num 1
> 
> 
> I simply don't know how extract that part which is im object (to convert 
> it next to spatialgriddataframe) or even only v (v I can insert to any 
> im object and next to convert it)
> 
> I hope that problem is trivial to more advanced R users
> 
> Jarek
> 
> 
> 
> 
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-- 
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Helleveien 30, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: Roger.Bivand at nhh.no