[R] filling a matrix with data

[antonio rodriguez]

aw2471 at bristol.ac.uk wrote:
> Hi,
> 
> I've extracted netcdf data in R, and am trying to output it in a matrix
> format.  I can make the matrix, and I have the data, but I can't get the
> matrix to include the data...
> 
> I'm not very experienced at using R, so please forgive the crudeness of
> these codes...
> 
> # For the matrix
> 
>  wind_dir_data<-matrix( NA, 17, 365 , byrow = FALSE )
> 
>  wind_speed_data<-matrix( NA, 17, 365, byrow = FALSE )
> 
> # to put the data into the matrix
> 
>  wind_dir_data[level, ]<-wind_dir_corrected
>  
>  wind_speed_data[level, ]<-rwind
> 
> #This is the response from R: "Error in "[<-"(`*tmp*`, level, , value =
> c(-0.889991788193583, -1.45999177545309,  : 
> 	number of items to replace is not a multiple of replacement length"
> 
> 
> If I try to call the data using wind_dir_data[1, ], i get a matrix full
> of NA, so the data hasn't transferred.  
> 
> Does anyone know what I'm doing wrong?
> 
> Many thanks,
> 
> Amy


Hope this helps:


library(netCDF)
rm(list=ls(all=TRUE))

#for example COADS data

sst<-read.netCDF("/home/toni/Tesis/COADS/sst.cdf")
str(sst)
a<-sst$"SST"
a[a == attributes(a)$"missing_value"] <- NA
dimnames(a) <- list(1:456,sst$"LAT125_128",sst$"LON351_355")
					^		^
					^		^
looking at str(sst) you get ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

note that 1:456 is the time length of your data


If you want to make a contour plot:

contour(a[1,,])

If you want to see the time series of a particular grid point (i.e. 
34.5n/350.5e):

plot((a[,"34.5","350.5"]),type="l")

a mean latitudinal value:

lat.mean <- apply(a,c(1,2),mean)

If you have 'NA's' :

sst.mean <- apply(a,c(2,3),mean,na.rm=T)


And, if you want a Matrix ;-)


F <- matrix(a,456,20) (456 months, 4x5 grid space = 20 cuadricules)


#                             <-   20 locations  ->
#                             -----------------------
#                         |   |                     |
#                         |   |                     |
#                         |   |                     |
#                         |   |                     |
#                         |   |                     |
#                         |   |                     |
#                         |   |                     |
#
#                     time ...                   ...
#
#                         |   |                     |
#                         |   |                     |
#                         |   |                     |
#                         |   |                     |
#                         |   |                     |
#                         |   |                     |
#                         V   |                     |
#                             -----------------------


Antonio

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