Hello
I am a new user of R .
and I ve problem with R and netcdf .
I succed installation , I could use all examples .
But when I take my netcf it is different .
I want to do statistic on this kind of file .
1)
first calculate mean .
my data is like that
through ncdump -h test.nc
netcdf test {
dimensions:
lat = 301 ;
lon = 401 ;
time = UNLIMITED ; // (80 currently)
variables:
float lat(lat) ;
lat:long_name = "latitude" ;
lat:standard_name = "latitude" ;
lat:units = "degrees_north" ;
lat:valid_range = -60., 60. ;
float lon(lon) ;
lon:long_name = "longitude" ;
lon:standard_name = "longitude" ;
lon:units = "degrees_east" ;
lon:valid_range = -100., 45. ;
double sst(time, lat, lon) ;
sst:long_name = "sea surface temperature" ;
sst:standard_name = "sea_surface_temperature" ;
sst:units = "K" ;
sst:_FillValue = -32768. ;
double time(time) ;
time:long_name = "time" ;
time:standard_name = "time" ;
time:units = "seconds since 1981-01-01 00:00:00" ;
time:ancillary_variables = "sst_data_processed_flag" ;
I succeed to read it with R, there is only one variable sst 80 days
and lat = 301 lon = 401 (this file is already a concatenation with
nco fonctions .
Here is what I do :
nc<-open.ncdf("test.nc")
summary (nc)
data<- get.var.ncdf(nc)
print (data)
answer extract :
[331,] -32768.00 -32768.00 -32768.00 -32768.00 -32768.00 -32768.00 -32768.00
[332,] -32768.00 -32768.00 -32768.00 -32768.00 -32768.00 -32768.00 -32768.00
[,295] [,296] [,297] [,298] [,299] [,300] [,301]
[1,] 0.10 0.10 0.12 0.15 0.15 0.14 0.15
[2,] 0.12 0.12 0.13 0.15 0.15 0.14 0.15
[3,] 0.13 0.13 0.13 0.16 0.14 0.14 0.14
[4,] 0.15 0.13 0.11 0.16 0.15 0.15 0.15
[5,] 0.17 0.16 0.15 0.15 0.16 0.17 0.15
#_fill_value is at -32768.00
[ reached getOption("max.print") -- omitted 69 row(s) and 79 matrix
slice(s) ] OK too long
> mean(data, na.rm=TRUE)
[1] -20020.35
> summary(data)
Min. 1st Qu. Median Mean 3rd Qu. Max.
-32770.00 -32770.00 -32770.00 -20020.00 0.42 6.59
> q()
It is clear that the missing value_FillValue = -32768. here , is used
to calculate the mean , the Median etc .
But I don't succed to avoid NA value in the sum ???
I've seen set.missval.ncdf but I don't succeed anymore to make R
understand that -32768 is a missing_value.
What are my mistakes , has someone an example or a solution ?
2)
Then after I want to calculate correlation between this one and another
one , so my time dimension is 80 (80 days) but my time variable is
always the same (because of concatenation with nco ) how can I
calculate cor(data1,data2)
and be sure that the correlation is not calculate between day1 and day50
for instance .
Thanks
Françoise Orain
.
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