MATLAB: How to calculate average values of one data according to specific indexes of same size

densitydepthindexesloop

Hi all,
I am intending to calculate average values of density(832695×1 double) according to depth indexes(832695×1 double), in order to obtain one single value of density for each 1 unit depth – elucidated by the table below.
I tried to find a solution applying the following loop; however the results have been not what I was expecting.
if depth_ind=round(depth);
for i=1:1:length(dens)-8
 if depth_ind(i)==depth_ind(i+8)     
     M(i)=(dens(i)+dens(i+1)+dens(i+2)+dens(i+3)+dens(i+4)+dens(i+5)+dens(i+6)+dens(i+7)+dens(i+8))/9;
 elseif depth_ind(i)==depth_ind(i+7)     
     M(i)=(dens(i)+dens(i+1)+dens(i+2)+dens(i+3)+dens(i+4)+dens(i+5)+dens(i+6)+dens(i+7))/8; 
 elseif depth_ind(i)==depth_ind(i+6)     
     M(i)=(dens(i)+dens(i+1)+dens(i+2)+dens(i+3)+dens(i+4)+dens(i+5)+dens(i+6))/7;
 elseif depth_ind(i)==depth_ind(i+5)     
     M(i)=(dens(i)+dens(i+1)+dens(i+2)+dens(i+3)+dens(i+4)+dens(i+5))/6;    
 elseif depth_ind(i)==depth_ind(i+4)     
     M(i)=(dens(i)+dens(i+1)+dens(i+2)+dens(i+3)+dens(i+4))/5;     
 elseif depth_ind(i)==depth_ind(i+3)     
     M(i)=(dens(i)+dens(i+1)+dens(i+2)+dens(i+3))/4;     
 elseif depth_ind(i)==depth_ind(i+2)   
     M(i)=(dens(i)+dens(i+1)+dens(i+2))/3;     
 elseif depth_ind(i)==depth_ind(i+1)
     M(i)=(dens(i)+dens(i+1))/2;     
 else 
     M(i)=dens(i);    
    end
end
How could I do that properly?
Thank you for your time,

Best Answer

X = [1 1021.714
1 1021.726
2 1021.736
2 1021.743 
2 1021.749
2 1021.755
2 1021.760
2 1021.765
3 1021.770
3 1021.774
3 1021.778
3 1021.781
3 1021.783
3 1021.787
3 1021.790];
ind = find(diff(X(:,1)) > 0);
ind1 = [1; ind+1];
ind2 = [ind; size(X,1)];
m = [];
for i=1:size(ind1)
  ind = ind1(i):ind2(i);
  m = [m; repmat(mean(X(ind, 2)), numel(ind), 1)];
end
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