Question

在my previous question的概括中，如何对单元格元素（即并且将保留数组本身）的加权平均值执行？

我首先要像这样修改gnovice's answer：

dim = ndims(c{1});          %# Get the number of dimensions for your arrays
M = cat(dim+1,c{:});        %# Convert to a (dim+1)-dimensional matrix
meanArray = sum(M.*weigth,dim+1)./sum(weigth,dim+1);  %# Get the weighted mean across arrays

在此之前，请确保weight具有正确的形状。我认为需要照顾的三个案例是

重量= 1（或任何常数）=＆gt;返回通常的平均值
numel（weight）== length（c）=＆gt;权重是每个单元格c {n}（但对于固定n的每个数组元素都相等）
numel（weight）== numel（cell2mat（c））=＆gt;每个数组元素都有自己的权重......

案例一很容易，案例3不太可能发生，所以我对案例2感兴趣：如何将权重转换为数组，使M.*weight在上面的总和中具有正确的维度？当然，一个答案显示了另一种获得加权平均值的方法。

编辑事实上，如果权重与c具有相同的结构，案例3甚至比案例1更为简单_{（重言式，道歉）}。

以下是我对案例2的意思的一个例子：

c = { [1 2 3; 1 2 3], [4 8 3; 4 2 6] };
weight = [ 2, 1 ];

应该返回

meanArray = [ 2 4 3; 2 2 4 ]

（例如，对于第一个元素（2 * 1 + 1 * 4）/（2 + 1）= 2）

Answer 1

熟悉REPMAT之后，现在这是我的解决方案：

function meanArray = cellMean(c, weight)
% meanArray = cellMean(c, [weight=1])
% mean over the elements of a cell c, keeping matrix structures of cell
% elements etc. Use weight if given.

% based on http://stackoverflow.com/q/5197692/321973, courtesy of gnovice
% (http://stackoverflow.com/users/52738/gnovice)
% extended to weighted averaging by Tobias Kienzler
% (see also http://stackoverflow.com/q/5231406/321973)

dim = ndims(c{1});          %# Get the number of dimensions for your arrays
if ~exist('weight', 'var') || isempty(weight); weight = 1; end;
eins = ones(size(c{1})); % that is german for "one", creative, I know...
if ~iscell(weight)
    % ignore length if all elements are equal, this is case 1
    if isequal(weight./max(weight(:)), ones(size(weight)))
        weight = repmat(eins, [size(eins)>0 length(c)]);
    elseif isequal(numel(weight), length(c)) % case 2: per cell-array weigth
        weight = repmat(shiftdim(weight, -3), [size(eins) 1]);
    else
        error(['Weird weight dimensions: ' num2str(size(weight))]);
    end
else % case 3, insert some dimension check here if you want
    weight = cat(dim+1,weight{:});
end;

M = cat(dim+1,c{:});        %# Convert to a (dim+1)-dimensional matrix
sumc = sum(M.*weight,dim+1);
sumw = sum(weight,dim+1);
meanArray = sumc./sumw;  %# Get the weighted mean across arrays

如何计算阵列单元阵列的加权平均值？

1 个答案: