In an assignment A(I) = B, the number of elements in B and I must be the same. while averaging row in Netcdf file

Hi,

I want to average the value of CO2 for a fixed height in fixed region in Netcdf file. I wrote code for single file. It's running fine and is given,

alti=ncread('SABER_L2C1.nc','altitude');
co2i=ncread('SABER_L2C1.nc','CO2retr');
timei=ncread('SABER_L2C1.nc','time');
lati=ncread('SABER_L2C1.nc','lat');
loni=ncread('SABER_L2C1.nc','lon');
datei=ncread('SABER_L2C1.nc','date');
       for i=1:size(lati,1);
        for j=1:size(alti,1);
            if lati(i) > -80 && lati(i) <0;
            if loni(i) >0 && loni(i) <100;
            lat(i)=lati(i);
            lon(i)=loni(i);
            if alti(j)==120;
                alt(j)=alti(j);
            co2a(j,i) = co2i(j,i);
            co2ab=mean(co2a,2);
            date1=mean(datei,1);
            end
            end
            end
        end
       end

When trying to do it for large number of files (~400) using cell, I am getting error "In an assignment A(I) = B, the number of elements in B and I must be the same". My code using cell is below, nc = cell(1, numfiles);

for k = 1:numfiles 
nc= netcdf.open(files(k).name); 
alti{k}=ncread(files(k).name,'altitude');
co2i{k}=ncread(files(k).name,'CO2retr');
timei{k}=ncread(files(k).name,'time');
lati{k}=ncread(files(k).name,'lat');
loni{k}=ncread(files(k).name,'lon');
datei{k}=ncread(files(k).name,'date');
end
for k=1:numfiles;
       for i=1:size(lati{k},1);
        for j=1:size(alti{k},1);
            if lati{k}(i) > -80 && lati{k}(i) <0;
            if loni{k}(i) >0 && loni{k}(i) <100;
            lat{k}(i)=lati{k}(i);
            lon{k}(i)=loni{k}(i);
            if alti{k}(j)==120;
                alt{k}(j)=alti{k}(j);
            co2a{k}(j,i) = co2i{k}(j,i);
            co2ab(k)=mean(co2a{k},2);
            date1(k)=mean(datei{k},1);
            end
   end

Need help. Thank you so much.

Answer 1

[Walter Roberson]

You have

            co2ab(k)=mean(co2a{k},2);
            date1(k)=mean(datei{k},1);

if co2a{k} or datei{k} are empty then you would have a problem. If they are vectors then you would be okay provided that co2a{k} is a row vector and datei{k} is a column vector. But if they are 2D arrays, then mean() is going to return a vector of values, and that vector is not going to fit into co2ab(k) or date1(k)

[Madan Kumar]

Thank you. co2a{k} or datei{k} are not empty, they are 2D arrays. In fact I need a single value of mean of co2a corresponding to a particular value of k. so I would get number of mean of co2a would be equal to number of k's. I tried everything I could but still problem persists.

[Walter Roberson]

Perhaps you want to use mean2()

[Madan Kumar]

As far as I know, mean2(A) would give mean of all the elements in matrix A. But I need only average of elements corresponding to alt=120, not all elements.

[Walter Roberson]

Mean of that row, or mean of that column?

mean(co2a{k}(j,:))   %perhaps

[Madan Kumar]

It should be mean of row. It worked. Thank you.