Hello,
A short code to include real monthly calendar to your data, similar to
the one inside NCEP2 reanalysis.
library(ncdf)
lon <- seq(from=140.0251, to=146.6751, length.out=241)
lat <- seq(from=-38.975, to=-31.025, length.out=160)
x=dim.def.ncdf("Lon","degreesE",as.double(lon))
y=dim.def.ncdf("Lat","degreesN",as.double(lat))
y1 = 1800 # start of the period
y2 = 2012 # end of the period
year <- seq(y1,y2,1)
day <-
c(31,28,31,30,31,30,31,31,30,31,30,31)%*%matrix(1,1,length(year));
day[2,leap.year(year)] <- 29; day <- as.vector(day)
hour <- day*24; hour <- c(hour[1],cumsum(hour[1:length(hour)-1]))
year <- rep(year,each=12)
syntime <- hour[year==1968] #change the year or change this line to
include more years
t=dim.def.ncdf("Time","hours since 1800-1-1 00:00:00",syntime,unlim=TRUE)
And your "mrain" matrix should have 3 dimensions (lon x lat x time),
before to save it as a NetCDF file.
Regards.
Le 04/07/2012 23:13, Jun Chen a écrit :
Hi Pascal,
I think I figure it out.
By doing the following, I can made "lon" & "lat" become a class of
dim.ncdf:
lon <- seq(from=140.0251, to=146.6751, length.out=241)
lat <- seq(from=-38.975, to=-31.025, length.out=160)
x=dim.def.ncdf("Lon","degreesE",as.double(lon))
y=dim.def.ncdf("Lat","degreesN",as.double(lat))
However, after running the script, there is a error I really unable to
understand:
error at data.frame(..., check.names = FALSE) :
parameter value mean different rows 0, 31981
If you can understand what the problem is, please as kind as offer me a
direction.
Many thanks,
Jun
Date: Wed, 4 Jul 2012 10:39:29 +0100
From: kri...@ymail.com
Subject: Re: [R] Please help
To: chensh...@hotmail.com
CC: r-help@r-project.org
Hello,
Following lines are wrong:
x=dim.def.ncdf("Lon","degreesE",140.0251:146.6751)
y=dim.def.ncdf("Lat","degreesN",(-31.025):(-38.975))
You have 241 longitudes and 160 latitudes.
lon <- seq(from=140.0251, to=146.6751, length.out=241)
lat <- seq(from=-38.975, to=-31.025, length.out=160)
Regards
----- Mail original -----
De : Jun Chen <chensh...@hotmail.com>
À : r-help@r-project.org
Cc :
Envoyé le : Mercredi 4 juillet 2012 10h52
Objet : [R] Please help
Dear All,
I am a research student in environment. I have only little
programming knowledge. I am currently doing the last project about rainfall
impact on ground water quality in an area. It happens that I have to use R to
read rainfall data (3 dimension) from ASC file (*.asc), and then write them
into one NCDF file (*.nc).
I have been working very hard on study R, but I still can not fix
the problem. Could someone please as kind as point out that what the problems
are in my R script?
Firstly, this is an example of data in asc file:
NCOLS 241
NROWS 160
XLLCORNER 140.00012207031
YLLCORNER -39.000000000000
CELLSIZE 0.50000000000000E-01
NODATA_VALUE -99.00000
166.30 160.87 155.23 149.33 143.83 138.52 133.29
128.34 123.76 119.21
115.06 110.90 107.22 103.69 100.40 97.29 94.58
92.15 90.00 87.91
86.20 84.57 83.22 81.94 81.11 80.38 79.37 78.73
79.70 79.62
-----------------------------------------------------------------------------------------------------------------------
And then this is the script I wrote:
setwd("E:/grid")
#defining dimension
x=dim.def.ncdf("Lon","degreesE",140.0251:146.6751)
y=dim.def.ncdf("Lat","degreesN",(-31.025):(-38.975))
t=dim.def.ncdf("Time","1968-01",1:12,unlim=TRUE)
#setup variable
varmr=var.def.ncdf("mr","mm",list(x,y,t),-99.00,
longname="monthly rainfall")
#create ncdf file
ncnew=create.ncdf("rainfall.nc", varmr)
#read input
files=list.files(pattern=".asc")
mrain=matrix(0:0,0,3)
for(i in files)
{rainfall=data.frame(readAsciiGrid(i))
mrain=cbind(mrain,rainfall)
}
put.var.ncdf(ncnew, mrain)
close.ncdf(ncnew)
-------------------------------------------------------------------------------
[[elided Hotmail spam]]
Many thanks,
Jun
[[alternative HTML version deleted]]
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