How to create feature vector in Scala? [duplicate] - scala

Question

This question already has an answer here:
How to transform the dataframe into label feature vector?
(1 answer)
Closed 5 years ago.
I am reading a csv as a data frame in scala as below:
+-----------+------------+
|x |y |
+-----------+------------+
| 0| 0|
| 0| 33|
| 0| 58|
| 0| 96|
| 0| 1|
| 1| 21|
| 0| 10|
| 0| 65|
| 1| 7|
| 1| 28|
+-----------+------------+
Then I create the label and feature vector as below:
val assembler = new VectorAssembler()
.setInputCols(Array("y"))
.setOutputCol("features")
val output = assembler.transform(daf).select($"x".as("label"), $"features")
println(output.show)
The output is as:
+-----------+------------+
|label | features |
+-----------+------------+
| 0.0| 0.0|
| 0.0| 33.0|
| 0.0| 58.0|
| 0.0| 96.0|
| 0.0| 1.0|
| 0.0| 21.0|
| 0.0| 10.0|
| 1.0| 65.0|
| 1.0| 7.0|
| 1.0| 28.0|
+-----------+------------+
But instead of this I want the output to be like in the below format
+-----+------------------+
|label| features |
+-----+------------------+
| 0.0|(1,[1],[0]) |
| 0.0|(1,[1],[33]) |
| 0.0|(1,[1],[58]) |
| 0.0|(1,[1],[96]) |
| 0.0|(1,[1],[1]) |
| 1.0|(1,[1],[21]) |
| 0.0|(1,[1],[10]) |
| 0.0|(1,[1],[65]) |
| 1.0|(1,[1],[7]) |
| 1.0|(1,[1],[28]) |
+-----------+------------+
I tried
val assembler = new VectorAssembler()
.setInputCols(Array("y").map{x => "(1,[1],"+x+")"})
.setOutputCol("features")
But did not work.
Any help is appreciated.

Answer 1

This is not how you use VectorAssembler.
You need to give the names of your input columns. i.e
new VectorAssembler().setInputCols(Array("features"))
You'll face eventually another issue considering the data that you have shared. It's not much a vector if it's one point. (your features columns)
It should be used with 2 or more columns. i.e :
new VectorAssembler().setInputCols(Array("f1","f2","f3"))