How can I average points with just the same x-coordinate?

I have many plots on top of each other, and there are a lot of points with the same x coordinate. I want to average all points same x coordinate, and plot this as one new point, so to get an idea of the general trend. Is there an easy way to do this in MATLAB?

Answer 1

[Sean de Wolski]

Sure!

% Sample x y
x = randi(10,100,1);
y = rand(100,1);

% Unique x's and their locations
[ux,~,idx] = unique(x);

% Accumulate 
ymean = accumarray(idx,y,[],@mean);

% Plot
plot(ux,ymean)

[Mert Ali Ihsan Kalin]

Thanks, exactly what I was looking for!

Answer 2

[Joseph Cheng]

if you have more than 1 plot as in >>plot(x,y) but more of >>plot(x1,y1,x2,y2) etc or a held plot then you can try this.

x1=1:1:20; y1=1:1:20; 
x2=1:2:20; y2=1:2:20;
x3=1:3:20; y3=1:3:20;
x4=1:4:20; y4=1:4:20;

%pre-allocate average y matrix
Y = zeros(max([length(x1) length(x2) length(x3) length(x4)]),4); 
Y(:,1) = y1;
[a b] = ismember(x1,x2);
Y(a,2) = y2;
[a b] = ismember(x1,x3);
Y(a,3) = y3;
[a b] = ismember(x1,x4);
Y(a,4) = y4;

av_Y = sum(Y,2)./sum(Y~=0,2);

[Joseph Cheng]

thinking about it more y could have zeros so swap out the corresponding lines

Y = nan(max([length(x1) length(x2) length(x3) length(x4)]),4); 
av_Y = nanmean(Y,2)