netcdf files in a predefined domain

Hello,

I am trying to read multiple netcdf4 files in a predefined area (lat and lon). I want values OUTSIDE my predefined area to be equal to '-99' but below code changes all the values to -99.

NOTE: in the below code lat_edge and lon_edge are lat and lon values from first satellite and sub_lat and sub_lon are lat and lon values from second satellite. I'm doing collocation first.

       lat_edge=double([min(lat(:)) max(lat(:))]); 
       lon_edge=double([min(lon(:)) max(lon(:))]);
       index_out_edge=find(sub_lat(:)<=lat_edge(1) | sub_lat(:)>=lat_edge(2) | sub_lon(:)<=lon_edge(1) | sub_lon(:)>=lon_edge(2));
       CLTT_temp = ncread(files{i},'CLTT'); 
       CLTT_temp_FINAL=CLTT_temp(min(row):max(row),min(col):max(col)); %min and max row col are lat lon indices from second satellite. 
       CLTT_temp_FINAL(index_out_edge)=-99;

kindly tell me what I'm missing in my code.

thank you.

[Walter Roberson]

What shows up for

nnz(sub_lat(:)>lat_edge(1) & sub_lat(:)<lat_edge(2) & sub_lon(:)>lon_edge(1) & sub_lon(:)<lon_edge(2))

If this shows up as 0 then every point was determined to be out of bounds.

[IMC]

Thank you.

Yeah it's 0.

[Walter Roberson]

What are

lat_edge
lon_edge
min(sub_lat(:)), max(sub_lat(:))
min(sub_lon(:)), max(sub_lon(:))

[IMC]

lat_edge = 12.3334 33.2646

lon_edge = 125.8553 152.3933

min(sub_lat(:)) = 15

max(sub_lat(:)) = 55

min(sub_lon(:)) = 80

max(sub_lon(:)) = 140

[Walter Roberson]

It looks like the distribution of your values might be biased. I suggest investigating with something like

lat_edge = double([min(lat(:)) max(lat(:))]); 
lon_edge = double([min(lon(:)) max(lon(:))]);

fill(lon_edge([1 2 2 1]), lat_edge([1 1 2 2]), [.5 .5 .5]);
hold on
scatter(sub_lon, sub_lat, [], 'r')
hold off
xlim auto
ylim auto

The red marks that show up in the mid-gray background are the ones that should be located by index_out_edge. My suspicion is that you will find all your marks are outside the rectangle.

[IMC]

Thank you

Answer 1

[KSSV]

Something like this should work:

index_out_edge = ~(((sub_lat(:)<=lat_edge(1) | sub_lat(:)>=lat_edge(2)) &&  (sub_lon(:)<=lon_edge(1) | sub_lon(:)>=lon_edge(2))));