Question

假设我有2个相同大小的输入向量x和reset

x = [1 2 3 4 5 6]
reset = [0 0 0 1 0 0]

和输出y，它是x中元素的累积和。每当重置的值对应于1时，元素的累积总和将重置并重新开始，如下所示

y = [1 3 6 4 9 15]

我如何在Matlab中实现这个？

Answer 1

diff和cumsum -

的一种方法

%// Setup few arrays: 
cx = cumsum(x)         %// Continuous Cumsumed version
reset_mask = reset==1  %// We want to create a logical array version of 
                       %// reset for use as logical indexing next up

%// Setup ID array of same size as input array and with differences between 
%// cumsumed values of each group placed at places where reset==1, 0s elsewhere
%// The groups are the islands of 0s and bordered at 1s in reset array.
id = zeros(size(reset))
diff_values = x(reset_mask) - cx(reset_mask)
id(reset_mask) = diff([0 diff_values])

%// "Under-compensate" the continuous cumsumed version cx with the 
%// "grouped diffed cumsum version" to get the desired output
y = cx + cumsum(id)

Answer 2

这是一种方式：

result = accumarray(1+cumsum(reset(:)), x(:), [], @(t) {cumsum(t).'});
result = [result{:}];

这是有效的，因为如果对accumarray的第一个输入进行排序，则会保留第二个输入的每个组中的顺序（更多关于此here）。

区间累积求和 - MATLAB

2 个答案: