matrix - MATLAB find and apply function to values of repeated indices -


i have 352x11 matrix, indexed column 1 10 data points. of index values repeated. i'd find repeated indices , calculate mean data points repeated trials (avoiding loops, if possible).

for example,

x =     26   77.5700   17.9735   32.7200    27   40.5887   16.6100   31.5800    28   60.4734   18.5397   33.6200    28   35.6484   27.2000   54.8000    29   95.3448   19.0000   37.7300    30   82.7273   30.4394   39.1400

to end with:

ans =     26   77.5700   17.9735   32.7200    27   40.5887   16.6100   31.5800    28   48.0609   22.8699   44.2150    29   95.3448   19.0000   37.7300    30   82.7273   30.4394   39.1400

i thinking if used

j = find(diff(x(:,1))==0);

to find position of repeated values, apply function corresponding positions of x, begin?

you can apply accumarray multiple columns as shown here

labels = x(:,1) - min(x(:, 1)) + 1;  labels = [repmat(labels(:),size(x,2),1), kron(1:size(x,2),ones(1,numel(labels))).'];              totals = accumarray(labels,x(:),[], @mean);

this adapted gnovice's code.

to work code need delete zeros in front

totals(find(mean((totals == zeros(size(totals)))')), :) = [];

which results in desired

   26.0000   77.5700   17.9735   32.7200    27.0000   40.5887   16.6100   31.5800    28.0000   48.0609   22.8699   44.2100    29.0000   95.3448   19.0000   37.7300    30.0000   82.7273   30.4394   39.1400

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