我有第二個問題圍繞Spark 2.1中的CosineSimilarity/ColumnSimilarities。我對scala和所有的Spark環境都很陌生,並且這對我來說並不是很清楚:columnSimilarities()返回Spark數據框
如何從spark中的rowMatrix中爲列的每個組合獲取ColumnSimilarities。這裏是我的嘗試:
數據:
import org.apache.spark.sql.{SQLContext, Row, DataFrame}
import org.apache.spark.sql.types.{StructType, StructField, StringType, IntegerType, DoubleType}
import org.apache.spark.sql.functions._
// rdd
val rowsRdd: RDD[Row] = sc.parallelize(
Seq(
Row(2.0, 7.0, 1.0),
Row(3.5, 2.5, 0.0),
Row(7.0, 5.9, 0.0)
)
)
// Schema
val schema = new StructType()
.add(StructField("item_1", DoubleType, true))
.add(StructField("item_2", DoubleType, true))
.add(StructField("item_3", DoubleType, true))
// Data frame
val df = spark.createDataFrame(rowsRdd, schema)
代碼:
import org.apache.spark.ml.feature.VectorAssembler
import org.apache.spark.mllib.linalg.distributed.{MatrixEntry, CoordinateMatrix, RowMatrix}
val rows = new VectorAssembler().setInputCols(df.columns).setOutputCol("vs")
.transform(df)
.select("vs")
.rdd
val items_mllib_vector = rows.map(_.getAs[org.apache.spark.ml.linalg.Vector](0))
.map(org.apache.spark.mllib.linalg.Vectors.fromML)
val mat = new RowMatrix(items_mllib_vector)
val simsPerfect = mat.columnSimilarities()
println("Pairwise similarities are: " + simsPerfect.entries.collect.mkString(", "))
輸出:
Pairwise similarities are: MatrixEntry(0,2,0.24759378423606918), MatrixEntry(1,2,0.7376189553526812), MatrixEntry(0,1,0.8355316482961213)
所以什麼時I g et is simsPerfect org.apache.spark.mllib.linalg.distributed.CoordinateMatrix
我的專欄和相似之處。我將如何將其轉換回數據框並獲得正確的列名稱?
我首選的輸出:
item_from | item_to | similarity
1 | 2 | 0.83 |
1 | 3 | 0.24 |
2 | 3 | 0.73 |
在此先感謝