how can i extract data from netcdf file for a given lat and long

Hi I am working with Matlab to extract pr variable for the entire time period from a netcdf file for a specific lat and long coordinates. My location has lat=36 and long=9.15. The netcdf file has a Latitude matrix of 453 X 453 and a Longitude matrix of 453 X 453. Variables: lon Size: 453x453 Dimensions: x,y Datatype: double Attributes: standard_name = 'longitude' long_name = 'longitude' units = 'degrees_east' lat Size: 453x453 Dimensions: x,y Datatype: double Attributes: standard_name = 'latitude' long_name = 'latitude' units = 'degrees_north' time Size: 1826x1 Dimensions: time Datatype: double Attributes: standard_name = 'time' units = 'days since 1949-12-01' calendar = 'gregorian' bounds = 'time_bnds' axis = 'T' long_name = 'time' pr Size: 453x453x1826 Dimensions: x,y,time Datatype: single Attributes: _FillValue = 1.000000020040877e+20 grid_mapping = 'Lambert_Conformal' standard_name = 'precipitation_flux' long_name = 'precipitation' units = 'kg m-2 s-1' cell_methods = 'time: mean' coordinates = 'lat lon' Now i would like to find the closest point in the Latitude and longitude matrix of the netcdf file to my actual lat and long coordinates. I did that using

d = (mylat-Latnetcdf).^2+(mylong-Longnetcdf).^2;
[~, ind] = min(d(:));
resultlat = lat(ind); %// use that index to obtain the result resultlong = long(ind);

but this returns ind=50049.

then, when i try to extract the pr variable from file using

ncread(netcdfname,'pr', [50049,50049, 1], [1 1 inf]);

it returns error

Error using netcdflib The NetCDF library encountered an error during execution of 'getVarsFloat' function - 'Index exceeds dimension bound (NC_EINVALCOORDS)'.

Error in netcdf.getVar (line 136) data = netcdflib(funcstr,ncid,varid,varargin{:});

Error in internal.matlab.imagesci.nc/read (line 635) data = netcdf.getVar(gid, varid, ...

Error in ncread (line 58) vardata = ncObj.read(varName, varargin{:});

can any one help please Thanks

[Chem]

Try this, although it can be very inefficient in terms of time, but it works

% Obtaining of points
% Latitude and Longitude
Puntos = single([-15, -70;...
                 -16, -71;]);
% Load netcdf data
Prec = ncread('Pisco_PP_Diario.nc','Prec'); 
lat = ncread('Pisco_PP_Diario.nc','Y'); 
lon = ncread('Pisco_PP_Diario.nc','X');
Dates = ncread('Pisco_PP_Diario.nc','T');

% Making the Grid
[GLat,GLon,GF] = meshgrid(lat,lon,Dates);

% Dimensioning
n = length(Puntos(:,1)); % number of rows or number of points
N = length(Dates);    % número de fechas (en días, meses, etc.) 
b = zeros(N,n);       % Number of dates (in days, months, etc.)   
for i = 1 : n
    a = double(interp3(GLat,GLon,GF,Prec,Puntos(i,1),Puntos(i,2),(Dates)));
    b(:,i) = reshape(a,length(a),1,[]);
end
for i = 1 : n
    subplot(n,1,i)
    plot(b(:,i),'LineWidth',1.5)
end

Answer 1

[Haifa Ben Romdhane]

%% Display the contents
fileName = 'g4.timeAvgMap.MODISA_L3m_CHL_2014_chla.20071201-20090531.47E_23N_58E_31N.nc';
ncdisp(fileName);

%% Read Info
info=ncinfo(fileName);
%Display variables name
nVar=size(info.Variables, 2);
disp('Variable names are:')
for ii=1:nVar
    disp(info.Variables(ii).Name);
end

%% Read variables
DATA  = ncread(fileName,'MODISA_L3m_CHL_2014_chla');
LAT = ncread(fileName,'lat');
LON = ncread(fileName,'lon');
 
%%Example
data=getValue(11.47916, 45.14583, LAT, LON, DATA);

Hi,

Try this code and the attached function. The example here is for Chlorophyll netcdf data.

Hope it helps!

[Shwarnali Bhattacharjee]

I tried this code. But , there is an error in the last part, mainly getValue, how can I resolve this?

Error: Undefined function 'getValue' for input arguments of type 'double'.

[Walter Roberson]

Haifa Ben Romdhane attached the code for getValue in their Answer. It has nothing to do with those toolboxes.

[negin soltani]

Hi,

I get this error when I run the code. I can't fix it