r循环迭代并找到每个项目之间的独特组合

Question

    concept_id                                  concept_name  event
1:     443387                    Malignant tumor of stomach comorb
2:    4193704 Type 2 diabetes mellitus without complication comorb
3:    4095320            Malignant tumor of body of stomach comorb
4:     201826                      Type 2 diabetes mellitus comorb
5:    4174977          Retinopathy due to diabetes mellitus comorb

对于上述数据，我正在尝试创建概念_ID组合的列表。有5个概念ID，因此当我们用另一个概念_ID迭代每个概念_ID时，我们会得到这样的列表。

nrow(comorb_event)
for (i in (1:nrow(comorb_event))) {
  for (j in (1:nrow(comorb_event))){
    print(paste(i,j))
  }
}

[1] "1 1"
[1] "1 2"
[1] "1 3"
[1] "1 4"
[1] "1 5"
[1] "2 1"
[1] "2 2"
[1] "2 3"
[1] "2 4"
[1] "2 5"
[1] "3 1"
[1] "3 2"
[1] "3 3"
[1] "3 4"
[1] "3 5"
[1] "4 1"
[1] "4 2"
[1] "4 3"
[1] "4 4"
[1] "4 5"
[1] "5 1"
[1] "5 2"
[1] "5 3"
[1] "5 4"
[1] "5 5"

我的输出不是我期望的。由于项目[1,1]是相同的项目，我们可以避免这种情况，并且[1,2]类似地，我们也可以删除该项目[2,1]。删除冗余组合后，预期列表将是这样的：

[1] "1 2"
[1] "1 3"
[1] "1 4"
[1] "1 5"
[1] "2 3"
[1] "2 4"
[1] "2 5"
[1] "3 4"
[1] "3 5"
[1] "4 5"

示例数据

structure(list(concept_id = c("443387", "4193704", "4095320", 
"201826", "4174977"), concept_name = c("Malignant tumor of stomach", 
"Type 2 diabetes mellitus without complication", "Malignant tumor of body of stomach", 
"Type 2 diabetes mellitus", "Retinopathy due to diabetes mellitus"
), event = structure(c(1L, 1L, 1L, 1L, 1L), .Label = c("comorb", 
"drug", "primary_dx"), class = "factor")), class = c("data.table", 
"data.frame"), row.names = c(NA, -5L), .internal.selfref = <pointer: 0x5642431689a0>)

Answer 1

我们需要combn

t(combn(seq_len(nrow(comorb_event)), 2))