R 所有可能的组合 [英] R all possible combinations

问题描述

我有空闲的数据框:

> my.df
          x         y
1 0.4597406 0.8439140
2 0.4579697 0.7461805
3 0.5593259 0.6646701
4 0.3607346 0.7792931
5 0.8377520 1.0445919
6 0.5597406 1.0445919

我想创建所有可能的组合

I want to create all possible combinations

> my.df
          x         y
1 0.4597406 0.8439140
2 0.4597406 0.7461805
3 0.4597406 0.6646701
4 0.4597406 0.7792931
5 0.4597406 1.0445919
6 0.4597406 1.0445919
7 0.4579697 0.8439140
8 0.4579697 0.7461805
9 0.4579697 0.6646701
... 
(Not all the combinations are showing here - This is to show the format that I would like to get the resulting data frame)

使用以下函数并没有真正给出确切的组合.

Using following functions didn't really give the exact combinations.

expand.grid(my.df)

生成所有可能组合的最佳方法是什么.

Whats the best way to generate all possible combinations.

推荐答案

expand.grid() 会给你所有可能的组合，但不是唯一的组合.如果你需要后者，你可以使用这样的函数

expand.grid() will give you all the possible combinations but not the unique combinations. If you need the latter you can use a function like this

unique_comb <- function(data){
   x.cur <- unique(data$x)
   y.cur <- unique(data$y)
   n.x <- length(x.cur)
   n.y <- length(y.cur)
   matrix.com <- matrix(0,ncol=2,nrow=n.x*n.y)
   ind <- 1
   for(i in 1:n.x){
       for(j in 1:n.y){
          matrix.com[ind,] <- c(x.cur[i],y.cur[j])
         ind <- ind+1
       }
   }
   return(matrix.com)
}

或者作为 JTT 点，这可以在一行中完成

Or as JTT points that this can be done in one line with

expand.grid(unique(data$x),unique(data$y)) 

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