R help - Mar 2006 - transform shapefiles in UTM to lat/long

Dear all:

I have a shapefile in UTM coordinate system and I would like to transform it
to Lat/Log coordinates (WSG84).  The package PBSmapping contains function
convUL to transform between the two coordinate systems when data is in the
form of a data frame with attributes specifying the coordinate system.
However, when shapefiles are imported using function read.shape (package
maptools), a list instead of a data frame is generated.  I could extract all
the polygons in the list and transform them, individually, but I hope there
is an easier way of doing that.  Besides, the shapefile i'm trying to
convert has two different UTM zones (is from Guatemala, and it covers zones
15 and 16).  Any sugestions would be greatly appreciated.

Thanks,

Fredy

	[[alternative HTML version deleted]]

On Tue, 21 Mar 2006, Fredy O. Mejia wrote:
> Dear all:
> 
> I have a shapefile in UTM coordinate system and I would like to transform
it
> to Lat/Log coordinates (WSG84).  The package PBSmapping contains function
> convUL to transform between the two coordinate systems when data is in the
> form of a data frame with attributes specifying the coordinate system.
> However, when shapefiles are imported using function read.shape (package
> maptools), a list instead of a data frame is generated.  I could extract
all
> the polygons in the list and transform them, individually, but I hope there
> is an easier way of doing that.  Besides, the shapefile i'm trying to
> convert has two different UTM zones (is from Guatemala, and it covers zones
> 15 and 16).  Any sugestions would be greatly appreciated.
My suggestion would be to read the shapefiles using the readOGR() function 
in the rgdal package, and then use the transform() method in that package 
to change from the appropriate UTM to geographical coordinates. 

Because I think your question involves more than that (I don't understand
how a single shapefile can use two UTM zones), I suggest moving this
thread to the R-sig-geo mailing list, and have cc-ed this reply there.

Please also say which platform and version of R you are using.
> 
> Thanks,
> 
> Fredy
> 
-- 
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

On Tuesday 21 March 2006 08:13 am, Fredy O. Mejia wrote:
> Dear all:
>
> I have a shapefile in UTM coordinate system and I would like to transform
> it to Lat/Log coordinates (WSG84).  The package PBSmapping contains
> function convUL to transform between the two coordinate systems when data
> is in the form of a data frame with attributes specifying the coordinate
> system. However, when shapefiles are imported using function read.shape
> (package maptools), a list instead of a data frame is generated.  I could
> extract all the polygons in the list and transform them, individually, but
> I hope there is an easier way of doing that.  Besides, the shapefile
i'm
> trying to convert has two different UTM zones (is from Guatemala, and it
> covers zones 15 and 16).  Any sugestions would be greatly appreciated.
>
> Thanks,
>
> Fredy
>
> 	[[alternative HTML version deleted]]
>
Fredy,

I would recommend performing the inverse projection with the GDAL/OGR library 
first. 


-- 
Dylan Beaudette
Soils and Biogeochemistry Graduate Group
University of California at Davis
530.754.7341

Hi R users:

When I use this commands:
-------------------------------------------------------------
testData<-read.table("testData.dat",header=T)
model1J<-glm(MCHNV~offset(Offset1),data=testData,family="poisson")
step(model1J,direction="forward",
     
scope=(list(upper=~IA+IM+altura+Region+Region:IA+Region:IM+Region:altura+offset(Offset1))))
-------------------------------------------------------------
(the "testData" (testData.dat) is attached to the e-mail to reproduce
the
problem):
I got this error:
-------------------------------------------------------------
.
.
.
  MCHNV ~ Region + IA + altura + offset(Offset1)

                 Df Deviance     AIC
+ IA:Region      8   540.24 1377.73
+ IM             1   586.84 1410.32
+ altura:Region  8   574.21 1411.70
<none>               600.74 1422.23

Step:  AIC= 1377.73
  MCHNV ~ Region + IA + altura + Region:IA + offset(Offset1)

Error in factor.scope(ffac, list(add = fadd, drop = fdrop)) :
         upper scope does not include model
-------------------------------------------------------------

What am I doing wrong?

I try also with:

step(model1J,direction="forward",
     
scope=(list(upper=~IA+IM+altura+Region+IA:Region+Region:IM+Region:altura+offset(Offset1))))

and with

step(model1J,direction="forward",
     
scope=(list(upper=~IA+IM+altura+Region+IA:Region+Region:IA+Region:IM+Region:altura+offset(Offset1))))

I got the same message

Thank you for your help.

Kenneth