Data sources

In this section, we introduce how to use data source in ML to load data. Besides some general data sources such as Parquet, CSV, JSON and JDBC, we also provide some specific data sources for ML.

Table of Contents

Image data source
LIBSVM data source

Image data source

This image data source is used to load image files from a directory, it can load compressed image (jpeg, png, etc.) into raw image representation via ImageIO in Java library. The loaded DataFrame has one StructType column: “image”, containing image data stored as image schema. The schema of the image column is:

origin: StringType (represents the file path of the image)
height: IntegerType (height of the image)
width: IntegerType (width of the image)
nChannels: IntegerType (number of image channels)
mode: IntegerType (OpenCV-compatible type)
data: BinaryType (Image bytes in OpenCV-compatible order: row-wise BGR in most cases)

ImageDataSource implements a Spark SQL data source API for loading image data as a DataFrame.

scala> val df = spark.read.format("image").option("dropInvalid", true).load("data/mllib/images/origin/kittens")
df: org.apache.spark.sql.DataFrame = [image: struct<origin: string, height: int ... 4 more fields>]

scala> df.select("image.origin", "image.width", "image.height").show(truncate=false)
+-----------------------------------------------------------------------+-----+------+
|origin                                                                 |width|height|
+-----------------------------------------------------------------------+-----+------+
|file:///spark/data/mllib/images/origin/kittens/54893.jpg               |300  |311   |
|file:///spark/data/mllib/images/origin/kittens/DP802813.jpg            |199  |313   |
|file:///spark/data/mllib/images/origin/kittens/29.5.a_b_EGDP022204.jpg |300  |200   |
|file:///spark/data/mllib/images/origin/kittens/DP153539.jpg            |300  |296   |
+-----------------------------------------------------------------------+-----+------+

ImageDataSource implements Spark SQL data source API for loading image data as a DataFrame.

Dataset<Row> imagesDF = spark.read().format("image").option("dropInvalid", true).load("data/mllib/images/origin/kittens");
imageDF.select("image.origin", "image.width", "image.height").show(false);
/*
Will output:
+-----------------------------------------------------------------------+-----+------+
|origin                                                                 |width|height|
+-----------------------------------------------------------------------+-----+------+
|file:///spark/data/mllib/images/origin/kittens/54893.jpg               |300  |311   |
|file:///spark/data/mllib/images/origin/kittens/DP802813.jpg            |199  |313   |
|file:///spark/data/mllib/images/origin/kittens/29.5.a_b_EGDP022204.jpg |300  |200   |
|file:///spark/data/mllib/images/origin/kittens/DP153539.jpg            |300  |296   |
+-----------------------------------------------------------------------+-----+------+
*/

In PySpark we provide Spark SQL data source API for loading image data as a DataFrame.

>>> df = spark.read.format("image").option("dropInvalid", True).load("data/mllib/images/origin/kittens")
>>> df.select("image.origin", "image.width", "image.height").show(truncate=False)
+-----------------------------------------------------------------------+-----+------+
|origin                                                                 |width|height|
+-----------------------------------------------------------------------+-----+------+
|file:///spark/data/mllib/images/origin/kittens/54893.jpg               |300  |311   |
|file:///spark/data/mllib/images/origin/kittens/DP802813.jpg            |199  |313   |
|file:///spark/data/mllib/images/origin/kittens/29.5.a_b_EGDP022204.jpg |300  |200   |
|file:///spark/data/mllib/images/origin/kittens/DP153539.jpg            |300  |296   |
+-----------------------------------------------------------------------+-----+------+

In SparkR we provide Spark SQL data source API for loading image data as a DataFrame.

> df = read.df("data/mllib/images/origin/kittens", "image")
> head(select(df, df$image.origin, df$image.width, df$image.height))

1               file:///spark/data/mllib/images/origin/kittens/54893.jpg
2            file:///spark/data/mllib/images/origin/kittens/DP802813.jpg
3 file:///spark/data/mllib/images/origin/kittens/29.5.a_b_EGDP022204.jpg
4            file:///spark/data/mllib/images/origin/kittens/DP153539.jpg
  width height
1   300    311
2   199    313
3   300    200
4   300    296

LIBSVM data source

This LIBSVM data source is used to load ‘libsvm’ type files from a directory. The loaded DataFrame has two columns: label containing labels stored as doubles and features containing feature vectors stored as Vectors. The schemas of the columns are:

label: DoubleType (represents the instance label)
features: VectorUDT (represents the feature vector)

LibSVMDataSource implements a Spark SQL data source API for loading LIBSVM data as a DataFrame.

scala> val df = spark.read.format("libsvm").option("numFeatures", "780").load("data/mllib/sample_libsvm_data.txt")
df: org.apache.spark.sql.DataFrame = [label: double, features: vector]

scala> df.show(10)
+-----+--------------------+
|label|            features|
+-----+--------------------+
|  0.0|(780,[127,128,129...|
|  1.0|(780,[158,159,160...|
|  1.0|(780,[124,125,126...|
|  1.0|(780,[152,153,154...|
|  1.0|(780,[151,152,153...|
|  0.0|(780,[129,130,131...|
|  1.0|(780,[158,159,160...|
|  1.0|(780,[99,100,101,...|
|  0.0|(780,[154,155,156...|
|  0.0|(780,[127,128,129...|
+-----+--------------------+
only showing top 10 rows

LibSVMDataSource implements Spark SQL data source API for loading LIBSVM data as a DataFrame.

Dataset<Row> df = spark.read.format("libsvm").option("numFeatures", "780").load("data/mllib/sample_libsvm_data.txt");
df.show(10);
/*
Will output:
+-----+--------------------+
|label|            features|
+-----+--------------------+
|  0.0|(780,[127,128,129...|
|  1.0|(780,[158,159,160...|
|  1.0|(780,[124,125,126...|
|  1.0|(780,[152,153,154...|
|  1.0|(780,[151,152,153...|
|  0.0|(780,[129,130,131...|
|  1.0|(780,[158,159,160...|
|  1.0|(780,[99,100,101,...|
|  0.0|(780,[154,155,156...|
|  0.0|(780,[127,128,129...|
+-----+--------------------+
only showing top 10 rows
*/

In PySpark we provide Spark SQL data source API for loading LIBSVM data as a DataFrame.

>>> df = spark.read.format("libsvm").option("numFeatures", "780").load("data/mllib/sample_libsvm_data.txt")
>>> df.show(10)
+-----+--------------------+
|label|            features|
+-----+--------------------+
|  0.0|(780,[127,128,129...|
|  1.0|(780,[158,159,160...|
|  1.0|(780,[124,125,126...|
|  1.0|(780,[152,153,154...|
|  1.0|(780,[151,152,153...|
|  0.0|(780,[129,130,131...|
|  1.0|(780,[158,159,160...|
|  1.0|(780,[99,100,101,...|
|  0.0|(780,[154,155,156...|
|  0.0|(780,[127,128,129...|
+-----+--------------------+
only showing top 10 rows

In SparkR we provide Spark SQL data source API for loading LIBSVM data as a DataFrame.

> df = read.df("data/mllib/sample_libsvm_data.txt", "libsvm")
> head(select(df, df$label, df$features), 10)

   label                      features
1      0 <environment: 0x7fe6d35366e8>
2      1 <environment: 0x7fe6d353bf78>
3      1 <environment: 0x7fe6d3541840>
4      1 <environment: 0x7fe6d3545108>
5      1 <environment: 0x7fe6d354c8e0>
6      0 <environment: 0x7fe6d35501a8>
7      1 <environment: 0x7fe6d3555a70>
8      1 <environment: 0x7fe6d3559338>
9      0 <environment: 0x7fe6d355cc00>
10     0 <environment: 0x7fe6d35643d8>

MLlib: Main Guide

MLlib: RDD-based API Guide

Data sources

Image data source

LIBSVM data source