问题描述
这是一个关于在同一个语句多次递增MATLAB阵列的一个值，而无需使用for循环的问题。
This is a question about incrementing one value of a MATLAB array multiple times in the same statement, without having to use a for loop.
设置我的数组：
>> A = [10 20 30];
然后运行：
>> A([1, 1]) = A([1, 1]) + [20 3]
A =
13 20 30
显然，20被忽略。不过，我想它被收录，因此：
Clearly the 20 is ignored. However, i would like it to be included, so that:
>> A = [10 20 30];
>> A([1, 1]) = A([1, 1]) + [20, 3]
会给：
A =
33 20 30
是否有一个功能，允许这种在一个不错的，矢量化的方式进行？
Is there a function to allow this to be done in a nice, vectorised fashion?
（在现实中，分度到阵列将包括多个索引，因此它可能是 [1 1 2 2 1 1 1 1 3 3 3] 等，与数字的数组，递增（即 [20,3] 以上）的长度相同。）
(In reality, the indexing to the array would include multiple indexes, so it could be [1 1 2 2 1 1 1 1 3 3 3] etc., with an array of numbers to increment by (the [20, 3] above) of the same length.)
推荐答案
你想做什么，可以使用函数的，像这样：
What you want to do can be done using the function ACCUMARRAY, like so:
A = [10 20 30]; %# Starting array
index = [1 2 2 1]; %# Indices for increments
increment = [20 10 10 3]; %# Value of increments
A = accumarray([1:numel(A) index].',[A increment]); %'# Accumulate starting
%# values and increments
和本实施例的输出应为：
And the output of this example should be:
A = [33 40 30];
结果
修改如果 A 是一个大阵的价值观，并有短短的增量增加，下面可能比计算效率更高上图：
If A is a large array of values, and there are just a few increments to add, the following may be more computationally efficient than the above:
B = accumarray(index.',increment); %'# Accumulate the increments
nzIndex = (B ~= 0); %# Find the indices of the non-zero increments
A(nzIndex) = A(nzIndex)+B(nzIndex); %# Add the non-zero increments
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