R-将dist函数应用于组 [英] R - Apply dist function to groups

问题描述

我正在尝试使用 dist()函数在R中按行排列，但是我得到的结果似乎根本就没有分组，它只是将dist()应用于我的所有数据框.

I am trying to apply the dist() function row wise in R but the result I get is as if it isn't grouping at all, it is simply applying dist() to all of my dataframe.

df2 %>% dplyr::group_by(X1) %>% dist()

df2是我的数据帧，为简单起见，我现在暂时申请.本质上，每个组都包含坐标(A，B)，我正在尝试获取每个点之间的距离.

Where df2 is my dataframe and I am just applying to the head for now, for simplicity. Essentially, each group contains coordinates (A,B) and I am trying to get the distance between each point.

这是我的数据框:

   X1  A              B
1   1  12             0.0
2   1  18             0.0
3   1  18             1.0
4   1  13             0.0
5   1  18             4.0
6   1  18             0.0
7   1  18             5.0
8   1  18             0.0
9   1  18             0.0
10  2  73            -2.0
11  2  73            -0.5
12  2  74            -0.5
13  2  73             0.0
14  2  71            -1.0
15  2  75             0.0

我想要的输出是每组的下三角矩阵，这是一个示例:

My desired output is the lower triangular matrix of each group, here is an example:

推荐答案

下面是创建物种物种虹膜数据集距离矩阵的示例

Here's an example of creating distance matrices of the iris data set by species

results = list()

for(spec in unique(iris$Species)){
  temp = iris[iris$Species==spec, 1:4]
  results[[length(results)+1]] = dist(temp)
}
names(results) = unique(iris$Species)

您必须弄清楚如何处理后遗症.

You'll have to figure out what to do with it afterwords.

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