What is a simple way to check if a collection of vectors all have the same number of elements
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I am look for a nice simple way to check if a collection of vectors all have the same number of elements. For example this might be used to validate some inputs to a function, or otherwise check compatibility before performing other operations.
Here's my current approach, which works, but I wonder if someone has simpler way of doing the same thing
a = rand(3,1);
b = rand(3,1);
c = rand(4,1);
d = rand(3,1);
vecs = {a,b,c,d};
n = cellfun(@numel,vecs);
if any(n(1)~=n)
error('all vectors must be same length')
end
2 个评论
Torsten
2023-9-22
Why not renaming a,b,c and d to vecs{1},vecs{2},vecs{3} and vecs{4} ? Should make things easier ...
Bruno Luong
2023-9-22
编辑:Bruno Luong
2023-9-22
I'm half serious but:
The simplest way? IMO just don't do any check, just rely on MATLAB, if any operation on vecs with incompatible sizes will imply error, just let MATLAB throw an error instead of
error('all vectors must be same length')
采纳的回答
Bruno Luong
2023-9-22
编辑:Bruno Luong
2023-9-22
if any(n(1)~=n)
The above will crash if your cell is empty.
IMO
if any(diff(n))
is a more robust test. Thus you can do the test in a single statement
if any(diff(cellfun(@numel,vecs)))
% ...
end
And last but not least, if performance matters, use this
if any(diff(cellfun('prodofsize',vecs)))
% ...
end
instead of @numel.
Here is why
vecs = arrayfun(@(x) zeros(randi(10),1), 1:1e6, 'unif', 0);
timeit(@()cellfun(@numel, vecs),1)
timeit(@()cellfun('prodofsize', vecs),1)
更多回答(1 个)
Walter Roberson
2023-9-22
a = rand(3,1);
b = rand(3,1);
c = rand(4,1);
d = rand(3,1);
vecs = {a,b,c,d};
n = cellfun(@numel,vecs,'uniform',0);
if ~isequal(n{:})
error('all vectors must be same length')
end
6 个评论
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