问题
i am looking for a way that i can add up elements in an array such that the first element of the first array is added to every element in the second array, then the second element in the first array is added to all every element in the second array and so on. The final vector will be length(a)*length(b) long
for example...
a=[1,2,3,4] b=[5,6,7]
answer =
[(1+5),(1+6),(1+7),(2+5),(2+6),(2+7),(3+5),(3+6),(3+7),(4+5),(4+6),(4+7)]
=[6,7,8,7,8,9,8,9,10,9,10,11]
回答1:
My first thought is to do this with arrayfun using an anonymous function that adds each scalar element of a to the full array in b. Then since you get a cell array result you can expand that cell array into the array you are looking for:
>> a=[1,2,3,4], b=[5,6,7]
>> result = arrayfun(@(x) x+b, a,'UniformOutput',false);
>> result = [result{:}]
result =
6 7 8 7 8 9 8 9 10 9 10 11
回答2:
Read up on bsxfun. It's very useful for this kind of things (and usually faster than arrayfun or for loops):
result = bsxfun(@plus, a(:).', b(:)); %'// matrix of size numel(b) x numel(a)
result = result(:).'; %'// linearize to a vector
Or, a little more freak: kron does what you want with products instead of sums. So:
result = log(kron(exp(a),exp(b)));
回答3:
Use meshgrid to create matrices of a and b and use matrix addition to compute a+b
a=[1,2,3,4], b=[5,6,7]
[A_matrix,B_matrix] = meshgrid(a,b)
result = A_matrix + B_matrix
result = result(:)'
来源：https://stackoverflow.com/questions/22158727/im-looking-for-a-way-to-add-up-elements-of-two-arrays