[英]How to find the vectors of the cell A that contain at least one element of the vector B?
How to find the vectors of A
that contain at least one element of the vector B
? 如何找到包含至少一个向量B
元素的A
向量?
example: 例:
A = {[2 5],[8 9 2],[33 77 4],[102 6],[10 66 17 7 8 11],[110 99],[1 4 3],[15 41 88]}
B = [5 77 41 66 7]
Result = {[2 5],[33 77 4],[10 66 17 7 8 11],[15 41 88]}
With arrayfun
and ismember
- 使用arrayfun
和ismember
-
Result = A(arrayfun(@(n) any(ismember(B,A{n})),1:numel(A)))
Or with arrayfun
and bsxfun
- 或者使用arrayfun
和bsxfun
-
Result = A(arrayfun(@(n) any(any(bsxfun(@eq,B(:),A{n}),2)),1:numel(A)))
Or with arrayfun
and setdiff
- 或者使用arrayfun
和setdiff
-
Result = A(arrayfun(@(n) numel(setdiff(B,A{n})) < numel(B),1:numel(A)))
Or with arrayfun
and intersect
- 或者使用arrayfun
和intersect
-
Result = A(arrayfun(@(n) ~isempty(intersect(B,A{n})),1:numel(A)))
One could also use cellfun
here, such that the four counterpart cellfun
based solutions end up like these - 人们也可以在这里使用cellfun
,这样四个基于cellfun
的对应解决方案最终会像这样 -
Result = A(cellfun(@(x) any(ismember(B,x)), A))
Result = A(cellfun(@(x) any(any(bsxfun(@eq,B(:),x),2)),A))
Result = A(cellfun(@(x) numel(setdiff(B,x)) < numel(B),A))
Result = A(cellfun(@(x) ~isempty(intersect(B,x)),A))
Taking different route [Using bsxfun
's masking capability] 采取不同的路线[使用bsxfun
的掩蔽能力]
Rather than going into those arrayfun
or cellfun
based approaches that are essentially loopy approaches, one can make the solution alot vectorized by converting A
into a 2D numeric array. 不是进入那些基本上是循环方法的基于arrayfun
或cellfun
的方法,而是可以通过将A
转换为2D数值阵列来使解决方案很多 。 So, the idea here is to have a 2D
array in which number of rows is the maximum number of elements in A
and number of columns as number of cells in A
. 因此,这里的想法是有一个2D
数组,其中行数是A
中元素的最大数量,列数是A
中单元格的数量。 Each column of this array would hold elements from each cell of A
and NaNs
would fill up the empty spaces . 该数组的每一列都将保存A
每个单元格中的元素,并且NaNs
将填充空白空间 。
The solution code with such an approach would look like this - 使用这种方法的解决方案代码看起来像这样 -
lens = cellfun('length',A); %// number of elements in each cell of A
mask = bsxfun(@ge,lens,(1:max(lens))'); %//'# mask of valid places in the 2D array
A_arr = NaN(size(mask)); %//initialize 2D array in which A elements are to be put
A_arr(mask) = [A{:}]; %// put the elements from A
%// Find if any element from B is in any element along the row or dim-3
%// locations in A_arr. Then logically index into A with it for the final
%// cell array output
Result = A(any(any(bsxfun(@eq,A_arr,permute(B,[1 3 2])),1),3));
>> celldisp(Result)
Result{1} =
2 5
Result{2} =
33 77 4
Result{3} =
10 66 17 7 8 11
Result{4} =
15 41 88
For people interested in seeing the runtime performances, here's a quick benchmarking test with a sufficiently huge datasize - 对于有兴趣了解运行时性能的人来说,这是一个快速的基准测试,具有足够大的数据量 -
%// Create inputs
N = 10000; %// datasize
max_num_ele = 100; %// max elements in any cell of A
num_ele = randi(max_num_ele,N,1); %// number of elements in each cell of A
A = arrayfun(@(n) randperm(N,num_ele(n)), 1:N, 'uni', 0);
B = randperm(N,num_ele(1));
%// Warm up tic/toc.
for k = 1:100000
tic(); elapsed = toc();
end
%// Start timing all approaches
disp('************************ With arrayfun **************************')
disp('------------------------ With arrayfun + ismember')
tic
Result = A(arrayfun(@(n) any(ismember(B,A{n})),1:numel(A)));
toc, clear Result
disp('------------------------ With arrayfun + bsxfun')
tic
Result = A(arrayfun(@(n) any(any(bsxfun(@eq,B(:),A{n}),2)),1:numel(A)));
toc, clear Result
disp('------------------------ With arrayfun + setdiff')
tic
Result = A(arrayfun(@(n) numel(setdiff(B,A{n})) < numel(B),1:numel(A)));
toc, clear Result
disp('------------------------ With arrayfun + intersect')
tic
Result = A(arrayfun(@(n) ~isempty(intersect(B,A{n})),1:numel(A)));
toc, clear Result
disp('************************ With cellfun **************************')
disp('------------------------ With cellfun + ismember')
tic
Result = A(cellfun(@(x)any(ismember(B,x)), A));
toc, clear Result
disp('------------------------ With cellfun + bsxfun')
tic
Result = A(cellfun(@(x) any(any(bsxfun(@eq,B(:),x),2)),A));
toc, clear Result
disp('------------------------ With cellfun + setdiff')
tic
Result = A(cellfun(@(x) numel(setdiff(B,x)) < numel(B),A));
toc, clear Result
disp('------------------------ With cellfun + setdiff')
tic
Result = A(cellfun(@(x) ~isempty(intersect(B,x)),A));
disp('************************ With masking bsxfun **************************')
tic
lens = cellfun('length',A); %// number of elements in each cell of A
mask = bsxfun(@ge,lens,(1:max(lens))'); %//'
A_numarr = NaN(size(mask));
A_numarr(mask) = [A{:}];
Result = A(any(any(bsxfun(@eq,A_numarr,permute(B,[1 3 2])),1),3));
toc
The results thus obtained on my system were - 在我的系统上获得的结果是 -
************************ With arrayfun **************************
------------------------ With arrayfun + ismember
Elapsed time is 0.409810 seconds.
------------------------ With arrayfun + bsxfun
Elapsed time is 0.157327 seconds.
------------------------ With arrayfun + setdiff
Elapsed time is 1.154602 seconds.
------------------------ With arrayfun + intersect
Elapsed time is 1.081729 seconds.
************************ With cellfun **************************
------------------------ With cellfun + ismember
Elapsed time is 0.392375 seconds.
------------------------ With cellfun + bsxfun
Elapsed time is 0.143341 seconds.
------------------------ With cellfun + setdiff
Elapsed time is 1.101331 seconds.
------------------------ With cellfun + setdiff
************************ With masking bsxfun ********************
Elapsed time is 0.067224 seconds.
As one can see, cellfun
based solutions are wee bit faster than their arrayfun
based counterparts! 正如人们所看到的, cellfun
基础的解决方案比他们快凌晨一点arrayfun
基于同行! Also, mask-based bsxfun
approach looks like an interesting one, but do keep in mind it's memory-hungry nature . 此外,基于掩码的bsxfun
方法看起来很有趣,但请记住它的内存饥饿性 。
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.