使用Java将Spark数据帧中的数组转换为DenseVector
我正在运行Spark 2.3。我想将以下数据帧中的列使用Java将Spark数据帧中的数组转换为DenseVector,java,apache-spark,dataframe,apache-spark-sql,user-defined-functions,Java,Apache Spark,Dataframe,Apache Spark Sql,User Defined Functions,我正在运行Spark 2.3。我想将以下数据帧中的列功能从ArrayType转换为DenseVector。我正在Java中使用Spark +---+--------------------+ | id| features| +---+--------------------+ | 0|[4.191401, -1.793...| | 10|[-0.5674514, -1.3...| | 20|[0.735613, -0.026...| | 30|[-0.030161237,
功能
从ArrayType
转换为DenseVector
。我正在Java中使用Spark
+---+--------------------+
| id| features|
+---+--------------------+
| 0|[4.191401, -1.793...|
| 10|[-0.5674514, -1.3...|
| 20|[0.735613, -0.026...|
| 30|[-0.030161237, 0....|
| 40|[-0.038345724, -0...|
+---+--------------------+
root
|-- id: integer (nullable = false)
|-- features: array (nullable = true)
| |-- element: float (containsNull = false)
我已经编写了以下UDF
,但它似乎不起作用:
private static UDF1 toVector = new UDF1<Float[], Vector>() {
private static final long serialVersionUID = 1L;
@Override
public Vector call(Float[] t1) throws Exception {
double[] DoubleArray = new double[t1.length];
for (int i = 0 ; i < t1.length; i++)
{
DoubleArray[i] = (double) t1[i];
}
Vector vector = (org.apache.spark.mllib.linalg.Vector) Vectors.dense(DoubleArray);
return vector;
}
}
运行此代码段时,我面临以下错误:
ReadProcessData$1不能强制转换为org.apache.spark.sql.expressions。用户定义聚合函数
问题在于如何在Spark中注册
udf
。您不应该使用UserDefinedAggregateFunction
,它不是用于聚合的udf
,而是udaf
。相反,你应该做的是:
spark.udf().register("toVector", toVector, new VectorUDT());
然后,要使用注册函数,请使用:
df3.withColumn("featuresnew", callUDF("toVector",df3.col("feautres")));
udf
本身应进行如下微调:
spark.udf().register("toVector", (UserDefinedAggregateFunction) toVector);
df3 = df3.withColumn("featuresnew", callUDF("toVector", df3.col("feautres")));
df3.show();
UDF1 toVector = new UDF1<Seq<Float>, Vector>(){
public Vector call(Seq<Float> t1) throws Exception {
List<Float> L = scala.collection.JavaConversions.seqAsJavaList(t1);
double[] DoubleArray = new double[t1.length()];
for (int i = 0 ; i < L.size(); i++) {
DoubleArray[i]=L.get(i);
}
return Vectors.dense(DoubleArray);
}
};
问题在于如何在Spark中注册
udf
。您不应该使用UserDefinedAggregateFunction
,它不是用于聚合的udf
,而是udaf
。相反,你应该做的是:
spark.udf().register("toVector", toVector, new VectorUDT());
然后,要使用注册函数,请使用:
df3.withColumn("featuresnew", callUDF("toVector",df3.col("feautres")));
udf
本身应进行如下微调:
spark.udf().register("toVector", (UserDefinedAggregateFunction) toVector);
df3 = df3.withColumn("featuresnew", callUDF("toVector", df3.col("feautres")));
df3.show();
UDF1 toVector = new UDF1<Seq<Float>, Vector>(){
public Vector call(Seq<Float> t1) throws Exception {
List<Float> L = scala.collection.JavaConversions.seqAsJavaList(t1);
double[] DoubleArray = new double[t1.length()];
for (int i = 0 ; i < L.size(); i++) {
DoubleArray[i]=L.get(i);
}
return Vectors.dense(DoubleArray);
}
};
@b工程师:对于Spark中的机器学习,向量(
DenseVector
,SparseVector
)用于输入,而不是数组。可能还有其他用例。@b工程师:对于Spark中的机器学习,向量(DenseVector
,SparseVector
)用于输入,而不是数组。还可能有其他用例。