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Belay Gebregiorgis

2012-May-19 09:49 UTC

[R] converting csv to image file

Hello everyone,

I want to get a 1km by lkm grid raster image using my csv data. If I call
latitude=a, longitude=b and preciptation=c.

a<-(1,2,3,4,5)
b<-(6,7,8,9,10)
c<-(10,20, 30,40, 50)

Then I found an example in r help which goes like

pts = read.table("file.csv",......)
library(sp)
library(rgdal)

proj4string(pts)=CRS("+init=epsg:4326") # set it to lat-long
pts = spTransform(pts,CRS("insert your proj4 string here"))
gridded(pts) = TRUE
r = raster(pts)
projection(r) = CRS("insert your proj4 string here")

Because I am new to R, I have no idea what to put into the proj4 string and
all that. Can anyone help me on this? If there is a different way of doing
this, that is also fine.

Kind Regards,

Belay

	[[alternative HTML version deleted]]

Simon Knapp

2012-May-19 11:22 UTC

head link

[R] converting csv to image file

provided you get the call to read.table (or perhaps read.csv) right
and presuming that file contains only the image data, you should
be able to say:

r <- raster(as.matrix(read.csv("file.csv")))
extent(r) <- extent(xmin, xmax, ymin, ymax)

and not worry about the projection (if it is plain old decimal degrees)

Regards,
Simon

On Sat, May 19, 2012 at 7:49 PM, Belay Gebregiorgis <belayg12 at
gmail.com> wrote:> Hello everyone,
>
> I want to get a 1km by lkm grid raster image using my csv data. If I call
> latitude=a, longitude=b and preciptation=c.
>
> a<-(1,2,3,4,5)
> b<-(6,7,8,9,10)
> c<-(10,20, 30,40, 50)
>
> Then I found an example in r help which goes like
>
> pts = read.table("file.csv",......)
> library(sp)
> library(rgdal)
>
> proj4string(pts)=CRS("+init=epsg:4326") # set it to lat-long
> pts = spTransform(pts,CRS("insert your proj4 string here"))
> gridded(pts) = TRUE
> r = raster(pts)
> projection(r) = CRS("insert your proj4 string here")
>
> Because I am new to R, I have no idea what to put into the proj4 string and
> all that. Can anyone help me on this? If there is a different way of doing
> this, that is also fine.
>
> Kind Regards,
>
> Belay
>
> ? ? ? ?[[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

Michael Sumner

2012-May-19 12:09 UTC

head link

[R] converting csv to image file

This already in your question:

"+init=epsg:4326"

That is equivalent to "+proj=longlat +ellps=WGS84" just looked up via
the
EPSG code. A good site to explore this topic is spatialreference.org

On Saturday, May 19, 2012, Belay Gebregiorgis wrote:
> Hello everyone,
>
> I want to get a 1km by lkm grid raster image using my csv data. If I call
> latitude=a, longitude=b and preciptation=c.
>
> a<-(1,2,3,4,5)
> b<-(6,7,8,9,10)
> c<-(10,20, 30,40, 50)
>
> Then I found an example in r help which goes like
>
> pts = read.table("file.csv",......)
> library(sp)
> library(rgdal)
>
> proj4string(pts)=CRS("+init=epsg:4326") # set it to lat-long
> pts = spTransform(pts,CRS("insert your proj4 string here"))
> gridded(pts) = TRUE
> r = raster(pts)
> projection(r) = CRS("insert your proj4 string here")
>
> Because I am new to R, I have no idea what to put into the proj4 string and
> all that. Can anyone help me on this? If there is a different way of doing
> this, that is also fine.
>
> Kind Regards,
>
> Belay
>
>        [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help@r-project.org <javascript:;> mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

-- 
Michael Sumner
Institute for Marine and Antarctic Studies, University of Tasmania
Hobart, Australia
e-mail: mdsumner@gmail.com

	[[alternative HTML version deleted]]

Belay Gebregiorgis

2012-May-20 12:41 UTC

head link

[R] converting csv to image file

Dear Simon,

I understand better now and it is running.

//Belay

On Sat, May 19, 2012 at 1:22 PM, Simon Knapp <sleepingwell@gmail.com>
wrote:
> I'm not sure what line you mean. The thing you pass to raster should
> be a matrix of the dimensions of your image data.
>
> You should have have xmin, xmax, ymin and ymax defined as something like:
>
> xmin <- min(x) - cw/2
> xmax <- max(x) + cw/2
> ymin <- min(y) - cw/2
> ymax <- max(y) + cw/2
>
> presuming that your x and y correspond to cell centres and where cw is
> your cell width (and if it is different in the two directions then you
> would 'cw.x' and 'cw.y'... if you know what I mean).
>
> Cheers,
> Simon
>
>
> On Sat, May 19, 2012 at 9:42 PM, Belay Gebregiorgis
<belayg12@gmail.com>
> wrote:
> > Thanks Simon. I have other vectors in the CSV file so after naming my
> > latitude and longitude x and y, I tried this. The first two lines run
> fine
> > but I get error in the second line.
> >
> >
> > r <- raster(as.matrix(F1))
> > extent(r) <- extent(xmin, xmax, ymin, ymax)
> > F1<-data.frame(x, y,z)
> >
> > Error in function (classes, fdef, mtable)  :
> >   unable to find an inherited method for function "extent",
for signature
> > "stand
> > Thankyou.
> >
> > Belay
> > On Sat, May 19, 2012 at 12:22 PM, Simon Knapp
<sleepingwell@gmail.com>
> > wrote:
> >>
> >> provided you get the call to read.table (or perhaps read.csv)
right
> >> and presuming that file contains only the image data, you should
> >> be able to say:
> >>
> >> r <- raster(as.matrix(read.csv("file.csv")))
> >> extent(r) <- extent(xmin, xmax, ymin, ymax)
> >>
> >> and not worry about the projection (if it is plain old decimal
degrees)
> >>
> >> Regards,
> >> Simon
> >>
> >> On Sat, May 19, 2012 at 7:49 PM, Belay Gebregiorgis
<belayg12@gmail.com
> >
> >> wrote:
> >> > Hello everyone,
> >> >
> >> > I want to get a 1km by lkm grid raster image using my csv
data. If I
> >> > call
> >> > latitude=a, longitude=b and preciptation=c.
> >> >
> >> > a<-(1,2,3,4,5)
> >> > b<-(6,7,8,9,10)
> >> > c<-(10,20, 30,40, 50)
> >> >
> >> > Then I found an example in r help which goes like
> >> >
> >> > pts = read.table("file.csv",......)
> >> > library(sp)
> >> > library(rgdal)
> >> >
> >> > proj4string(pts)=CRS("+init=epsg:4326") # set it to
lat-long
> >> > pts = spTransform(pts,CRS("insert your proj4 string
here"))
> >> > gridded(pts) = TRUE
> >> > r = raster(pts)
> >> > projection(r) = CRS("insert your proj4 string
here")
> >> >
> >> > Because I am new to R, I have no idea what to put into the
proj4
> string
> >> > and
> >> > all that. Can anyone help me on this? If there is a different
way of
> >> > doing
> >> > this, that is also fine.
> >> >
> >> > Kind Regards,
> >> >
> >> > Belay
> >> >
> >> >        [[alternative HTML version deleted]]
> >> >
> >> > ______________________________________________
> >> > R-help@r-project.org mailing list
> >> > https://stat.ethz.ch/mailman/listinfo/r-help
> >> > PLEASE do read the posting guide
> >> >
http://www.R-project.org/posting-guide.html<http://www.r-project.org/posting-guide.html>
> >> > and provide commented, minimal, self-contained, reproducible
code.
> >
> >
>
	[[alternative HTML version deleted]]

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