How to make a raster image in R from my own data set
Hi Kristi,
it takes a few extra steps to create a raster layer from your example
data set, as it is not a gridded map in Lat lon (probably in some
projection though). How exactly to do it depends on your data, but here
are some hints:
1. If you actually need to read the data set from a link, then
read.table.url is depreceted, just use read.table. You might need to
call setInternet2(TRUE) first, as the example data is on an https-url.
2. Raster can read a range of inputs, but I am not sure if .csv is one
of them, and definitely not if the data is not gridded. You can then
first do interpolation with a Spatial*-object. Set the coordinates of
your object, this creates a Spatial*-object, and add the projection:
coordinates(pts) = ~lon+lat
proj4string(pts) = CRS("+proj=longlat +datum=WGS84")
3. You will have to create your reference grid (spsample, from raster,
or another existing grid you have available), and interpolate to this
grid, using one of the many interpolation packages, such as geoR,
automap, gstat, intamap.
4. The resulting object can easily be converted to raster through
raster(interpolationResult[,resultname])
I hope this can help you getting started.
Generally you get quicker response to spatial questions from the
r-sig-geo list.
Jon
On 24-Apr-13 16:56, Kristi Glover wrote:
Hi R-user,
I was trying to make a raster map with WGS84 projection in R, but I could not make it. I found one data set in Google that data is almost the same format as of mine. I wanted to make a raster map of temperature with 1 degree spatial resolution for the global scale.
I could make it in GIS software but I do have many variables (to be many raster images) and ultimately I am importing them to R for further analysis. Therefore, I wanted to make them in R, if possible.
It would be great if you give some hints on how script look like in creating a raster map from my own data set (I have provided link for your references, this is an example data set).
I am really appropriating for your help.
#--------------------------------------------------
#create a raster map from scratch
install.packages("raster", dependencies=TRUE)
library(raster) # raster data
install.packages("rgdal", dependencies=TRUE)
library(rgdal) # input/output, projections
install.packages("rgeos", dependencies=TRUE)
library(rgeos) # geometry ops
install.packages("spdep", dependencies=TRUE)
library(spdep) # spatial dependence
install.packages("pastecs", dependencies=TRUE)
library(pastecs)
pts<-read.table.url("https://www.betydb.org//miscanthusyield.csv", header=T, sep=",")
proj4string(pts)=<- CRS("+proj=longlat +datum=WGS84")
#---------------------------------------------------------------------------
Cheers,
Kristi
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Jon Olav Sk?ien Joint Research Centre - European Commission Institute for Environment and Sustainability (IES) Land Resource Management Unit Via Fermi 2749, TP 440, I-21027 Ispra (VA), ITALY jon.skoien at jrc.ec.europa.eu Tel: +39 0332 789206 Disclaimer: Views expressed in this email are those of the individual and do not necessarily represent official views of the European Commission.