用案例选择 [英] Selecting with Cases

问题描述

请考虑：

Subsets[Flatten[ParallelTable[{i, j}, {i, 1, 96}, {j, 1, 4}], 1], {4}]

我需要选择所有子列表使得i值在每个子列表中从不相同4

I need to select all the Sublist such that the the i value is never the same within each sublist of 4

{{3,1}，{4,1}，{5,1} {{1,1}，{1,2}，{2,3}，{6,1}}应该被拒绝接受{6,1}}。我的价值1被重复了2次。

{{3,1},{4,1},{5,1},{6,1}} should be accepted while {{1,1},{1,2},{2,3},{6,1}} should be rejected. The Value 1 for i being repeated 2 times.

我知道我可以用Cases来做，但是不要理解它的语法，并找到关于案例的帮助相对于其潜在的应用程序来说，相当空白。

I know I could do this with Cases, but don`t understand the Syntax of it, and find the help on Cases rather empty compared to its potential applications.

推荐答案

假设您的数据位于变量数据，以下应该这样做：

Assuming your data is in the variable data, the following should do it:

Select[data, Length@Union[#[[All, 1]]] === 4 &]

这需要 / code> - 值（即第一个元素），并检查4个值是否全部不同（即，如果我们删除重复项，我们仍然有4个）

This takes the "i"-value (i.e. first element), and checks that the 4 values are all different (i.e. if we remove the duplicates we still have 4 of them)

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