Question

由于方法foo中的奇怪行为，我不能写像bar这样的方法，我需要的是：

import breeze.linalg.DenseMatrix
import breeze.linalg.DenseVector

class Test {

    val dim = 3
    val X:DenseMatrix[Double] = DenseMatrix.rand(dim,dim)
    val u:DenseVector[Double] = DenseVector.fill(dim){1.0}

    def foo:Unit = {

        val i=0;
        val row_i:DenseVector[Double] = X(i,::).t  // OK
        val s = u(i)+u(i)                          // OK

        val j:Integer = 0
        val row_j:DenseVector[Double] = X(j,::).t  // does not compile (A)
        val a = u(j)+u(j)                          // does not compile (B)
    }
    def bar(i:Integer):Double = u(i)+u(i)          // does not compile (C)
}

有解决方法吗？提前感谢所有回复。

编译错误：

（A）找不到参数canSlice的隐含值：       breeze.linalg.support.CanSlice2 [breeze.linalg.DenseMatrix [双]，整型collection.immutable。::。类型，结果]       没有足够的方法适用于方法:(隐式canSlice：   breeze.linalg.support.CanSlice2 [breeze.linalg.DenseMatrix [双]，整型collection.immutable。::。类型，结果]）


导致特质TensorLike。未指定的值参数canSlice。

（B），（C）

找不到参数canSlice的隐含值： breeze.linalg.support.CanSlice [breeze.linalg.DenseVector [双]，整型结果] 方法适用的参数不足:(隐式canSlice：breeze.linalg.support.CanSlice [breeze.linalg.DenseVector [Double]，Integer，Result]）结果特质TensorLike。未指定的值参数canSlice。

Answer 1

First off: convert your Integer to Int . That would take care of at least the first compilation error. Following update to your code does compile

import breeze.linalg.DenseMatrix
import breeze.linalg.DenseVector
import breeze.linalg.DenseMatrix
import breeze.linalg.DenseVector

class Test {

    val dim = 3
    val X:DenseMatrix[Double] = DenseMatrix.rand(dim,dim)
    val u:DenseVector[Double] = DenseVector.fill(dim){1.0}

    def foo:Unit = {

        val i=0;
        val row_i:DenseVector[Double] = X(i,::).t  // OK
        val s = u(i)+u(i)                          // OK

        val j:Int = 0
        val row_j:DenseVector[Double] = X(j,::).t  // does not compile (A)
        val a = u(j)+u(j)                          // does not compile (B)
    }
    def bar(i:Int):Double = u(i)+u(i)          // does not compile (C)
}

From the repl:

// Exiting paste mode, now interpreting.

import breeze.linalg.DenseMatrix
import breeze.linalg.DenseVector
defined class Test

So your other errors also disappear for me (scala 2.11.8). Let me know if you have further issues.

scala breeze矩阵切片和矢量索引需要解决方法

1 个答案: