[R-sig-Geo] Reading an Ascii file

Thu Jan 15 15:42:11 CET 2009

Dear Kamran,

this solution works fine for me but I have noticed that plot() does not work on the resulting dataframe. I am trying to read a variety of shape files and raster data sets into R for the purpose of running a model using the geographic info as inputs. I am using readOGR and plot() for my other shapefiles. What do I need to do to the SpatialGridDataFrame created in your script in order to use plot()  ? 

Sorry to ask such simplistic questions, but I am not that familar yet with with R or spatial analysis.

many thanks and best wishes,

Juliane 

 Dr. Juliane Struve
Environmental Scientist
10, Lynwood Crescent
Sunningdale SL5 0BL
01344 620811 

----- Original Message ----
From: Kamran Safi <kamran.safi at ioz.ac.uk>
To: "van Etten, Jacob (IRRI)" <J.vanEtten at cgiar.org>; Robert Hijmans <r.hijmans at gmail.com>
Cc: R-sig-Geo at stat.math.ethz.ch
Sent: Thursday, 15 January, 2009 9:20:04
Subject: Re: [R-sig-Geo] Reading an Ascii file

Good comment, and actually if the number of lines should be important, I can do it in two lines ;-)

library(maptools)
table <- data.frame(readAsciiGrid("<your file and its path>"))

I realized that you don't need rgdal.

Kamran

-----Original Message-----
From: r-sig-geo-bounces at stat.math.ethz.ch on behalf of van Etten, Jacob (IRRI)
Sent: Thu 15.01.2009 08:34
To: Robert Hijmans
Cc: R-sig-Geo at stat.math.ethz.ch
Subject: Re: [R-sig-Geo] Reading an Ascii file

The case for a as.data.frame(signature=RasterStack) method (then you
would have three lines (one less than Kamran)

-----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 Kamran Safi
Sent: Thursday, January 15, 2009 3:28 PM
To: Robert Hijmans; Juliane Struve
Cc: R-sig-Geo at stat.math.ethz.ch
Subject: Re: [R-sig-Geo] Reading an Ascii file

Hi all,

This should deliver the results Julie is looking for:

library(rgdal)
library(maptools)
grid <- readAsciiGrid("<your file and its path>")
table <- data.frame(grid)

That was it! Replace s1 and s2 with X and Y.

Kamran

------------------------
Kamran Safi

Postdoctoral Research Fellow
Institute of Zoology
Zoological Society of London
Regent's Park
London NW1 4RY

http://www.zoo.cam.ac.uk/ioz/people/safi.htm

http://spatialr.googlepages.com
http://asapi.wetpaint.com

-----Original Message-----
From: r-sig-geo-bounces at stat.math.ethz.ch on behalf of Robert Hijmans
Sent: Thu 15.01.2009 03:13
To: Juliane Struve
Cc: R-sig-Geo at stat.math.ethz.ch
Subject: Re: [R-sig-Geo] Reading an Ascii file

Dear Julie,

This is one way to do that, using the raster package (under
development):

install.packages("raster",
repos="http://R-Forge.R-project.org<http://r-forge.r-project.org/>
")

require(raster)
r <- rasterFromFile("d:/alt.asc", TRUE)
xy <- xyFromCell(r, 1:ncells(r))
xyv <- cbind(xy, values(r))

xyv[1:10,]

# To get rid of the NAs

xyv <- na.omit(xyv)
xyv[1:10,]

On Thu, Jan 15, 2009 at 1:01 AM, Juliane Struve
<juliane_struve at yahoo.co.uk>wrote:

> Dear list,
>
> I am trying to read ArcGIS raster data sets into R after converting
them
> into ASCII .txt file. The text file I am trying to read contains
>
> ncols        250
> nrows        276
> xllcorner    344147.19411119
> yllcorner    3024657.6122834
> cellsize      0.19970250725746
> NODATA_value  -9999
>
> in the first lines followed by a grid of values that are either -9999
or 1.
>
> I have used read.table("myfile.txt") which yields this (first 10
lines).
>
>
> V1            V2
> 1          ncols  2.500000e+02
> 2          nrows  2.760000e+02
> 3      xllcorner  3.441472e+05
> 4      yllcorner  3.024658e+06
> 5      cellsize  1.997025e-01
> 6      NODATA_value -9.999000e+03
> 7          -9999 -9.999000e+03
> 8          -9999 -9.999000e+03
> 9          -9999 -9.999000e+03
> 10        -9999 -9.999000e+03
>
> I would like to have the data as a table with coordinates for each
cell and
> the actual value.
>
> Could somebody advise me which function I should use ?
>
> Many thanks,
>
> Juliane
>
>
>
>
> _______________________________________________
> 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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