How to solve Error using griddedInterpolant The grid vectors are not strictly monotonic increasing?

Dear all

I want to regrid my netcdf file from 0.5*0.5 degree to 0.25*0.25 degree. I using this code below:

filename='precip.mon.total.v2018.nc';
ncdisp(filename)       
lat = ncread(filename,'lat');     
lon = ncread(filename,'lon');  
precip = ncread(filename,'precip');
t = ncread(filename,'time');
lat=double(lat);
lon=double(lon);
precip=double(precip);
t=double(t);
index=find(precip==-9.969209968386869e+36);
precip(index)=nan;

ds = 0.25 ;
loni = min(lon):ds:max(lon) ;
lati = min(lat):ds:max(lat) ;

[Loni,Lati] = meshgrid(loni,lati) ;

[latgrid,longrid] = meshgrid(lat,lon);

size(lat)
size(lon)
size(precip)

F=griddedInterpolant({lat,lon,t},precip);
newpreceip=F({lati,loni,t});

when I run this code my command windows show this:

Source:
           C:\Users\Behzad\Desktop\precip.mon.total.v2018.nc
Format:
           netcdf4_classic
Global Attributes:
           Original_Source = 'http://www.dwd.de/en/FundE/Klima/KLIS/int/GPCC/GPCC.htm
                              is the webpage and the data is at ftp://ftp.dwd.de/pub/data/gpcc/download.html'
           Reference       = 'Users of the data sets are kindly requested to give feed back and to refer to GPCC publications on this webpage: http://www.dwd.de/bvbw/appmanager/bvbw/dwdwwwDesktop/?_nfpb=true&_pageLabel=_dwdwww_klima_umwelt_datenzentren_wzn&T12404518261141645246564gsbDocumentPath=Content%2FOeffentlichkeit%2FKU%2FKU4%2FKU42%2Fteaser__product__access.html&_state=maximized&_windowLabel=T12404518261141645246564&lastPageLabel=_dwdwww_klima_umwelt_datenzentren_wzn'
           original_source = 'ftp://ftp-anon.dwd.de/pub/data/gpcc/html/fulldata_download.html'
           Conventions     = 'CF 1.0'
           dataset_title   = 'Global Precipitation Climatology Centre (GPCC)'
           References      = 'https://www.esrl.noaa.gov/psd/data/gridded/data.gpcc.html'
           title           = 'GPCC Full Data Reanalysis Version 2018 0.5x0.5 Monthly Total'
           history         = 'Created 09/2018  based on V2018 data obtained via ftp'
           data_modified   = '2019-03-12'
           _NCProperties   = 'version=2,netcdf=4.6.3,hdf5=1.10.5'
Dimensions:
           lat   = 360
           lon   = 720
           nbnds = 2
           time  = 1512  (UNLIMITED)
Variables:
    lat   
           Size:       360x1
           Dimensions: lat
           Datatype:   single
           Attributes:
                       long_name          = 'Latitude'
                       units              = 'degrees_north'
                       standard_name      = 'latitude'
                       axis               = 'Y'
                       coordinate_defines = 'point'
                       actual_range       = [89.75       -89.75]
    lon   
           Size:       720x1
           Dimensions: lon
           Datatype:   single
           Attributes:
                       long_name          = 'Longitude'
                       units              = 'degrees_east'
                       standard_name      = 'longitude'
                       actual_range       = [0.25        359.75]
                       axis               = 'X'
                       coordinate_defines = 'point'
    time  
           Size:       1512x1
           Dimensions: time
           Datatype:   double
           Attributes:
                       long_name          = 'Time'
                       units              = 'days since 1800-1-1 00:00:00'
                       delta_t            = '0000-01-00 00:00:00'
                       avg_period         = '0000-01-00 00:00:00'
                       standard_name      = 'time'
                       axis               = 'T'
                       coordinate_defines = 'start'
                       actual_range       = [33237  79227]
    precip
           Size:       720x360x1512
           Dimensions: lon,lat,time
           Datatype:   single
           Attributes:
                       missing_value = -9.969209968386869e+36
                       units         = 'mm'
                       var_desc      = 'Precipitation'
                       level_desc    = 'Surface'
                       parent_stat   = 'Observations'
                       long_name     = 'GPCC Monthly total of precipitation'
                       valid_range   = [0  8000]
                       statistic     = 'Total'
                       level         = 'Surface'
                       actual_range  = [0      4552.4302]
                       dataset       = 'GPCC Precipitation 0.5degree V2018 Full Reanalysis'
ans =
   360     1
ans =
   720     1
ans =
         720         360        1512
Error using griddedInterpolant
The grid vectors are not strictly monotonic increasing.
Error in test100 (line 50)
F=griddedInterpolant({lat,lon,t},precip); 

please help me how to fix this error and regrid my data.

netcdf file can be download from link below:

ftp://ftp.cdc.noaa.gov/Datasets/gpcc/full_v2018/precip.mon.total.v2018.nc

thank you all

Answer 1

[darova]

Error using griddedInterpolant
The grid vectors are not strictly monotonic increasing.

Maybe it's because of lat? It's decreasing

Variables:
    lat   
    %% -----
                       actual_range       = [89.75       -89.75]

Try to switch it

lati = max(lat):-ds:min(lat) ;

[BN]

Dear darova

thank you for your answer. unfortunately the problem still exists even when I switch to use what you mention above.

do you have any other idea?

best regards

[darova]

What is third parameter? Do you have radius?

[BN]

are you ask about nbnds?

no I don't have radius they are geographical coordinates.

latitude - longitude- time- and precipitation is all my variables. so precipitation dimension is = lat*lon*time

I want to regrid my precipitation data based on lat and lon, without changing time.

[darova]

Can you please attach the data in .mat file?

The data you want to re-grid