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How to create nc file having lat, long, time, and 2D matrix

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Jitesh Dadich
Jitesh Dadich on 4 Apr 2019
Answered: ANKUR KUMAR on 9 May 2019
Helo everyone,
I am trying to create a .nc file which will have lat, long, time and 2D matrix simultaneously.
I have loaded lat, long, and time parameters , but how will I put the corresponding 2D matrix for each lat long and time while creating .nc file.
The answer should come in a matrix which has time in 1st column, lat and long in 1st & 2nd rows, and parameter values corresponding to time and lat_long.
Thank you in advance

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Accepted Answer

KSSV
KSSV on 4 Apr 2019
Refer this demo example:
% nc filename to be written
file = 'myfile.nc' ;
%% Write lon and lat variables
% Get data
lon = 1:10 ;
lat = 1:10 ;
nx = length(lon) ;
nccreate(file,'lon','Dimensions',{'lon',1,nx},'DeflateLevel',7) ;
ny = length(lat) ;
nccreate(file,'lat','Dimensions',{'lat',1,ny},'DeflateLevel',7) ;
nccreate(file,'time','Dimensions',{'time',1,Inf},'DeflateLevel',7) ;
nccreate(file,'z','Dimensions',{'lon','lat','time'},'DeflateLevel',7) ;
for i = 1:10
ncwrite(file,'time',i,i) % write time
data = rand(10) ;
ncwrite(file,'z',data,[1,1,i]) ; % write 3D data
end

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Jitesh Dadich
Jitesh Dadich on 5 Apr 2019
This is 0.5 x 0.5 grid data.
we can't use linspace syntax.
The thing is lat and long are varying from 8.5 to 32 and 70 to 95.5, and total range of lat and lon is 785, respectively i.e. the data are irregular & they are in first 2 rows. Rest of the matrix have corresponding values (4270 x 785)
Is there any option I can create nc file.
thank you for helping me KSSV
Jitesh Dadich
Jitesh Dadich on 5 Apr 2019
Here I have attached a small file of my excel file.
Time is varying from 3rd row to 52 row in 1 st column and first 2 row has lon and lat.

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More Answers (1)

ANKUR KUMAR
ANKUR KUMAR on 9 May 2019
I hope this helps.
[data]=xlsread('test.csv');
lat=data(2,2:end);
lon=data(1,2:end);
vardata=data(3:end,2:end);
vardata(:,size(vardata,2)+1)=nan; %dummy column just to put nan over the points where data is not available
longitude=unique(lon);
latitude=unique(lat);
[lon_m,lat_m]=meshgrid(longitude,latitude);
index=arrayfun(@(x,y) find(lon==x & lat==y),lon_m,lat_m,'uni',0);
index(cellfun('isempty',index))={-9999.99};
datavar=str2double(string(index)); datavar(datavar==-9999.99)=786;
out=arrayfun(@(x) reshape(vardata(x,datavar),[48 51]),1:50,'uni',0);
outputdata=cat(3,out{:});
nccreatewrite('test.nc','lat',{'lat','c'},latitude')
nccreatewrite('test.nc','lon',{'lon','c'},longitude')
nccreatewrite('test.nc','TC',{'lat','lon','days'},outputdata)
You can check the validity of the above data by typing
squeeze(outputdata(latitude==32,longitude==75.5,:))
The output of the above line is the same as the second column in the excel file (of course by skipping the first two rows).

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