[英]Create all vector combinations summing up to a specific number in R
I am trying to create a matrix with two combinations of the same vector that sum up to 2300. I am using the combn
function in R, see the code below: 我正在尝试创建一个矩阵,其中两个矢量具有相同的组合,总和为2300。我在R中使用
combn
函数,请参见以下代码:
vector <- 400:1900
combinations <- combn(vector, 2, function(x) subset(x, sum(x)==2300))
Unfortunately, this code is not working. 不幸的是,此代码无法正常工作。 I get the following error:
我收到以下错误:
Error in combn(r2, 2, function(x) subset(x, sum(x) == 2300)) :
dims [product 1125750] do not match the length of object [0]
Do anyone know what i did wrong? 有人知道我做错了吗? Many thanks,
非常感谢,
Gion ion园
Try this: 尝试这个:
combinations <- combn(vector,2,function(x) ifelse(sum(x[1], x[2])==2300,
list(c(x[1],x[2])), list(c(0,0))))
res <- combinations[lapply(combinations, sum)>0]
head(res)
# [[1]]
# [1] 400 1900
# [[2]]
# [1] 401 1899
# [[3]]
# [1] 402 1898
# [[4]]
# [1] 403 1897
# [[5]]
# [1] 404 1896
# [[6]]
# [1] 405 1895
If you want to get a matrix of that: 如果要获取该矩阵:
matrix(unlist(res), ncol = 2, byrow = TRUE)
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