列表与LT;列表与LT;双>>为JAMA或其他库双重[] [] [英] List<List<Double>> to double[][] for JAMA or other libs

问题描述

我无法让我的列表>双重[] []工作在线性代数包，如 JAMA 的。
基本上我有一些类似这样的坐标列表：

i cannot get my List> to double[][] to work on linear algebra package like JAMA. Basically i have some sort of List with coordinates like this :

[[2.63, 11.087, -12.054], 
[2.357, 13.026, -15.29], 
[1.365, 16.691, -15.389], 
[0.262, 18.241, -18.694]]

我正在尝试将这些坐标放在 JAMA 类是double [] []。
我试图使用方法toArray，但是我失败了。

And i am trying to put these coordinates to JAMA class which is double[][]. I tried to use method toArray, but i failed.

double[][] array = list.toArray(new double[list.size()][]);

如何做？或者还有其他套餐可以应付SVD，这里需要使用列表吗？

How to do that? Or is there other packages to cope with SVD, which i need here, using List of Lists?

推荐答案

番石榴有一个双重类，其中有一个 toArray 需要一个 Collection<？扩展Number> ，从而获取列表< Double> 并转换为数组。所以...

Guava has a Doubles class which has a toArray that takes a Collection<? extends Number> and will thereby take a List<Double> and convert to an array. So...

List<List<Double>> myList;
double[][] myArray = new double[myList.size()][];
for (int i=0, n<myList.size(); i<n; i++){
     myArray[i] = Doubles.toArray(myList.get(i));
}

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