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我像这样构建一个Scala框架，例如

import org.saddle._
import scala.util.Random

val rowIx = Index(0 until 200)
val colIx = Index(0 until 100)

// create example having 15% of NaNs
val nanPerc = 0.15
val nanLength = math.round(nanPerc*rowIx.length*colIx.length).toInt
val nanInd = Random.shuffle(0 until rowIx.length*colIx.length).take(nanLength)
val rawMat = mat.rand(rowIx.length, colIx.length)
// contents gives a single array in row major
val rawMatContents = rawMat.contents
nanInd foreach { i => rawMatContents.update(i, Double.NaN) }

val df = Frame(rawMat, rowIx, colIx)

// now I'd like to test that the number of NaNs is correct but 
// most functions for this purpose in Frame e.g. countif exclude NaNs
df.???

计算 NaN 数量的最惯用的（Scala、Saddle）方法是什么？

4

2 回答 2

1

Frame.countif 实现为：

def countif(test: T => Boolean)(implicit ev: S2Stats): Series[CX, Int] = frame.reduce(_.countif(test))

而Vec.countif 实现为：

def countif(test: Double => Boolean): Int = r.filterFoldLeft(t => sd.notMissing(t) && test(t))(0)((a,b) => a + 1)

我们可以使用相同的方法，但删除test并反转 NaN 检查：

vec.filterFoldLeft(x => x.isNaN)(0)((a, b) => a + 1)

要在 a 上运行它Frame：

frame.reduce(_.filterFoldLeft(x => x.isNaN)(0)((a, b) => a + 1))
于 2017-09-25T12:54:23.857 回答
0

我找到了一个非常简单直接的方法：

retDf.toMat.contents.filter(x => x.isNaN).length
于 2017-09-25T12:40:45.767 回答