combining two image files into one database

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/>

--
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