MATLAB: Plotting in for loop not working. Averaging matrix over ranges.

averagingfor loop

I thought i had a code that worked but i noticed a tiny error, and ive been banging my head on a brick wall sleeplessly trying to get it to work for days.
Heres my code, i hate it, it doesn't work, if you reckon you can fix it please tell me otherwise just skip this bit and as I've decide to start again.
function TempSalplot(datafile)
datafile=importdata(datafile);
A=datafile.data;
figure;
col = flipud(parula(round(max(datafile.data(:,28)))));
%depth,distance,salinity,temp are in column 28,2,14,11 of datafile respectively;  
    for d=[1:3:max(datafile.data(:,28))]; %max is around 16
        for avd=[1:length(A(:,28))];
            if A(avd,28)>d-0.5 & A(avd,28)<d+0.5;
            B(avd,1)=A(avd,2);
            B(avd,2)=A(avd,14);
            B(avd,3)=A(avd,11);
            B(all(B==0,2),:)=[];
            end 
        [M,~,z] = unique(B(:,1),'stable');
        M(:,2) = accumarray(z,B(:,2),[],@mean);
        M(:,3) = accumarray(z,B(:,3),[],@mean);
        plot(M(:,2),M(:,3),'o-','color',col(d,:));
        hold on;  
        end
    xlabel('Salinity (psu)');
    ylabel('Tempurature (degC)');
    h=colorbar('ticks',[1:3:round(max(datafile.data(:,28)))]);
    h.Label.String=('Depth (m)');
    caxis([1,max(d)]);
    colormap(col);
end
Essentially i have 4 columns of interest say (a,b,c,d). I would like to average b and c over certain ranges of d. so I would only have as many b,c pairs for a certain d range as there are a values. Then I would like to plot that and redo it for another a range.
data=
0 15 33 0.5
0 15 32 0.8
0 16 32 1.3
0 13 34 1.6
10 13 34 0.6
10 14 35 1.0
10 16 36 1.5
10 12 33 1.9
25 13 34 0.6
25 12 33 0.9
25 12 34 1.6
25 12 36 1.9
What I think I need is a for loop.
1st iteration for 0<d=<1 (d=0.5).
M=
0 15 32.5 0.5
10 13.5 34.5 0.5
25 12.5 33.5 0.5
plot(M(:,2),M(:,3));
then repeat for d=1.5 (1<d=<2) however some of the later iteration for example (10<d=<11) have no measurements for certain values of a so should be shorter than the earlier iterations and therefore plot fewer points.
Any help on this is really appreciated , this has been a nightmare for me, thinking I had it working so many times.

Best Answer

It is easy to split your data into groups according to the fourth column:
B = [...
0 15 33 0.5
0 15 32 0.8
0 16 32 1.3
0 13 34 1.6
10 13 34 0.6
10 14 35 1.0
10 16 36 1.5
10 12 33 1.9
25 13 34 0.6
25 12 33 0.9
25 12 34 1.6
25 12 36 1.9];
% Vector of the edges of each group:
D = 0:2;
% Set figure colormap befor the loop:
set(0,'DefaultAxesColorOrder',winter(numel(D)-1))
% Iterate over each group:
for k = 2:numel(D)
    % Logical index for this group:
    X = D(k-1)<B(:,4) & B(:,4)<=D(k);
    % Calculate means for this group:
    [M,~,z] = unique(B(X,1));
    M(:,4) = accumarray(z,B(X,4),[],@mean);
    M(:,3) = accumarray(z,B(X,3),[],@mean);
    M(:,2) = accumarray(z,B(X,2),[],@mean);
    % Display info (optional):
    fprintf('From %d to %d\n',D(k-1),D(k))
    disp(M)
    % Plot:
    plot(M(:,2),M(:,3))
    hold all
end
which displays this in the command window:
From 0 to 1
    0.00000   15.00000   32.50000    0.65000
   10.00000   13.50000   34.50000    0.80000
   25.00000   12.50000   33.50000    0.75000
From 1 to 2
    0.00000   14.50000   33.00000    1.45000
   10.00000   14.00000   34.50000    1.70000
   25.00000   12.00000   35.00000    1.75000
And creates this figure:
Note that I do not have the colormap parula, so I used winter instead.
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