[R-sig-Geo] combining two image files into one database

Alok K Bohara, PhD bohara at unm.edu
Thu Jan 8 16:43:22 CET 2009 

Hi Tomislav:

I tried what you suggested, and it works for the first part with the 
built-in data example "bei.extra". (By the way, my script could not find 
achan.asc file????)

Anyway, for me, I actually wanted to build the bei.extra type file 
itself which contains a list of pixel images "elev"  and "grad". 

To replicate this, I took X_im and Y_im (two pixel image files)

X_im <- im(....)
Y_im <- im(...)

Now, I want to create/save  a file "XY.extra" that contains a list of 
two pixel images X_im and Y_im.

Thanks.

Alok





Tomislav Hengl wrote:
> Dear Alok,
>
> Maybe you should consider converting the im data to sp class. Then, you have as many grids in a
> single SpatialGridDataFrame e.g.:
>
>   
>> library(maptools)
>> library(rgdal)
>> grids <- as(bei.extra[[1]], "SpatialGridDataFrame")
>> names(grids)[1] <- "elev"
>> grids$grad <- as(bei.extra[[2]], "SpatialGridDataFrame")$v
>> spplot(grids["elev"])
>>     
> ...
>   
>> grids$achan <- readGDAL("achan.asc")$band1
>> save(grids, "grids.image")
>>     
>
> see also: http://spatial-analyst.net/wiki/index.php?title=Species_Distribution_Modelling 
>
> HTH,
>
> T. Hengl
>
>
>   
>> -----Original Message-----
>> From: r-sig-geo-bounces at stat.math.ethz.ch [mailto:r-sig-geo-bounces at stat.math.ethz.ch] On Behalf
>> Of Alok K. Bohara, PhD
>> Sent: Wednesday, January 07, 2009 4:21 PM
>> To: Greg Lee
>> Cc: r-sig-geo at stat.math.ethz.ch
>> Subject: Re: [R-sig-Geo] combining two image files into one database
>>
>> Thanks Greg for your response:
>>
>> I want to do what the examples in Spatstat do with regard to the point
>> and pixel/image data bei and bei.extra.. (bei.extra contains a list of
>> two image files --elevation and gradient.  They plot these two items
>> (and also take log, I believe)
>>
>> In my case:
>>
>> X_image
>> Y_image
>>
>> (I converted  both from text matrix to pixel/image using  "im(...)" command)
>>
>> I want to combine (or list) X_image and Y.image as a part of a single
>> file -- XY_image, and save and do the following
>>
>> load("XY.image")
>>
>> plot(XY_image)    # plot both images side by side
>> plot(XY_image$X_image)   # plot just the X_image
>> etc...
>>
>> Thank you for your help.
>>
>> #########
>>
>> I tried doing the list command:
>> XY_image <-list(X_image,Y_image)
>>
>> but it returns NULL when I do  "XY$X_image"
>>
>> Sincerely,
>> Alok Bohara
>>
>>
>>
>>
>>
>> Greg Lee wrote:
>>     
>>> Hello Alok,
>>>
>>> We really need more details about what you are trying to acheive in
>>> order to help you.
>>>
>>> c(X, Y) concatenates the objects X and Y. The result will be a vector.
>>> If X and Y happen to be m x n matrices, the result will be a vector of
>>> length 2 * m * n: probably not what you want.
>>>
>>> You can see this for yourself. Eg:
>>>
>>> X <- matrix(1, 3, 3)
>>> Y <- matrix(2, 3, 3)
>>> c(X, Y)
>>>
>>> If you were hoping to combine the information in corresponding pixels
>>> of the matrices X and Y, you will need to have a clear idea of *how*
>>> you would like the information to be combined. ie: Are you looking for
>>> the mean value of the pixels, or is some other operation required?
>>>
>>> Eg 2:
>>>
>>> X <- matrix(1:9, 3, 3)
>>> Y <- matrix(2, 3, 3)
>>> X + Y / 2
>>>
>>> Hope that helps.
>>>
>>> Greg
>>>
>>>
>>> 2009/1/7 Alok K. Bohara, PhD <bohara at unm.edu <mailto:bohara at unm.edu>>
>>>
>>>     Hi:
>>>
>>>     Let me start by saying that I am new to R.  I converted two pixel
>>>     ascii matrices into image files:
>>>
>>>     X_im <- im(X)   # X is an ascii pixel matrix
>>>     Y_im <- im(Y)  # Y is an ascii pixel matrix
>>>
>>>     How can I combine these two images into 1) one datafile "XY_im",
>>>     2) save it  and 3) read it after loading (e.g., x <- XY_im$X_im.
>>>     and plot it.)
>>>
>>>     I tried doing this:
>>>
>>>     XY_im <- c(X_im,Y_im)
>>>     save(XY _im, file = "XM_im.Rdata")
>>>     load("XY_im.Rdata")
>>>     x<- XY_im$X_im    # It does not like $ and says it is atomic
>>>     something...
>>>     plot(x)  # of course it does not work either.
>>>
>>>     What am I doing wrong?  Any tips?
>>>
>>>     Thanks you.
>>>
>>>     Alok Bohara
>>>
>>>
>>>     --
>>>     Alok K. Bohara, Ph.D.
>>>     Professor
>>>     Department of Economics
>>>     University of New Mexico
>>>     Albuquerque, NM 87131,USA
>>>     Ph: 505-277-5903/5304(w)
>>>     Fax:505-277-9445
>>>     email: bohara at unm.edu <mailto:bohara at unm.edu>
>>>     http://www.unm.edu/~econ/faculty/professors.html
>>>     <http://www.unm.edu/%7Eecon/faculty/professors.html>
>>>     Nepal Study Center: http://nepalstudycenter.unm.edu
>>>     <http://nepalstudycenter.unm.edu/>
>>>
>>>     _______________________________________________
>>>     R-sig-Geo mailing list
>>>     R-sig-Geo at stat.math.ethz.ch <mailto:R-sig-Geo at stat.math.ethz.ch>
>>>     https://stat.ethz.ch/mailman/listinfo/r-sig-geo
>>>
>>>
>>>       
>> --
>> Alok K. Bohara, Ph.D.
>> Professor
>> Department of Economics
>> University of New Mexico
>> Albuquerque, NM 87131,USA
>> Ph: 505-277-5903/5304(w)
>> Fax:505-277-9445
>> email: bohara at unm.edu
>> http://www.unm.edu/~econ/faculty/professors.html
>> Nepal Study Center: http://nepalstudycenter.unm.edu
>>
>> _______________________________________________
>> R-sig-Geo mailing list
>> R-sig-Geo at stat.math.ethz.ch
>> https://stat.ethz.ch/mailman/listinfo/r-sig-geo
>>     
>
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>   


-- 
Alok K. Bohara, Ph.D.
Professor
Department of Economics
MSC 05 3060
1 University of New Mexico
Albuquerque, NM 87131-0001, USA
Ph: 505-277-5903/5304(w)
Fax:505-277-9445
email: bohara at unm.edu
http://www.unm.edu/~econ/faculty/professors.html
Nepal Study Center: http://nepalstudycenter.unm.edu

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