MATLAB: Logical indexing for row-wise average

MATLABmean

How can I get a row-wise mean of this matrix

      1 2 3
  A = 4 5 6
      7 8 9

but I only want to select these entries

      0 1 1
  B = 1 1 0
      1 0 1

so the result would be something like

      2.5
  C = 4.5
      8.0

Actually, this is easily possible with a loop, but I'd prefer a 1-line code. (this one is just a question of beauty :-))

Best Answer

 C=sum(A.*B,2)./sum(B,2);

Related Solutions

MATLAB: Bhilding new matrix with selected index number

just use b as an index vector :

a = [9;1;3;2;5;6;8;1;2;5;8;2];
b = [4;6;1];
c=zeros(1,length(a));
c(b) = a(b);

MATLAB: Interpolate gridded matrix row-wise

Normally you could achieve this easily by interpolating over rows with a function that does not extrapolate by default. I believe interp1 could do this (?). I used a slighly more messy approach, where I drew a polygon around the area of interest, filled all nans, then removed all points outside of the polygon.

Z = sst_up_574;
X = Y1;
Y = Ydepth;
%Scan rows and find first non-NaN
x = nan(size(X,1))
y = nan(size(Y,1))
for j = 1:size(Z,1)
    [~,c] = find(~isnan(Z(j,:))==true,1,'first');
    if ~isempty(c)
        x(j) = X(j,c);
        y(j) = Y(j,c);
    else
        x(j) = max(X(j,:));
        y(j) = max(Y(j,:));
    end
end
x(isnan(x))=[];
y(isnan(y))=[];
%Build a polygon
x = [x 0];
y = [y min(Y(:))]
%Find points inside of polygon
in = inpolygon(X(:),Y(:),x,y);
%Fill all NaNs
Zq = fillmissing(Z,'linear',2);
%Set values outside of polygon to NaN
Zq(~in) = NaN;
figure(1)
pcolor(X,Y,Zq); shading flat
set(gca,'Ydir','reverse')
set(gca,'xlim',[bin(1) bin(91)],...
    'ylim',[0 500],'fontsize',8,'xminortick','on','yminortick','on')
hold on
hc = colorbar;
rmap=jet(20);
newmap=rmap(2:1:20,:);
colormap(newmap);
caxis([4 23]);
grid on;
box on
set(gca,'Fontweight','bold','Fontsize',16);
set(get(hc,'ylabel'),'string','Water Temperature (^oC)','rotation',270,'verticalalignment','bottom');
ylabel('Depth (m)');
xlabel('Date');
title(['Water Temperature: Upstream SG574'], 'fontweight', 'bold','FontSize',18)

Best Answer

Related Solutions

MATLAB: Bhilding new matrix with selected index number

MATLAB: Interpolate gridded matrix row-wise

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