Today we learned the implementation of chained invocation styles in Scala, and in spark programming we often see the following code:Sc.textfile ("hdfs://..."). FlatMap (_.split ("")). Map (_,1). Reducebykey (_ + _) ...This style of programming is called chained invocation, and its implementation is described in the following code:Class Animal {def Breathe:this.type = this}Class Cat extends Animal {def eat:t
Write a test code using Scala:Object= {println ("helloWorld") }}Consider this test as a class, the project organization structure such as:Then set the compile options:The compiled jar package can then be found under the project folder:Copied to the directory specified by Spark (built by yourself):Start Spark, and then submit the task:Spark-submit--class Test--master
Spark problem more than one Scala library found in the build path
There was an error building spark on Eclipse of window:
More than one Scala library found in the build path (d:/1win7/eclipse/plugins/org.scala-lang.scala-library_2.11.7. V20150622-112736-1fbce4612c.jar, G:/149/spa
Recently, when processing data, you need to join the raw data with Redis data, in the process of reading Redis, encountered some problems, by the way to make a note, hoping for other students also helpful. During the experiment, it was not stressful to read Redis one at a time when the amount of data was 100,000 levels, but when the amount of data reached tens, the problem arose, even with the mappartitions of Spark. Therefore, consider using Redis's
Today, Mr. Wang studied the function of pattern matching in Scala from the source point of view. Let's look at this pattern match in the source code:From the code we can see that case Registerworker (Id,workerhost,........) {} Here is a pattern match, and our pattern-matching class registerworker before it is defined, such as:We can see that our pattern matching class is already defined, and when our master receives a message from the worker, it makes
Jdk7Http://www.oracle.com/technetwork/java/javase/downloads/jdk7-downloads-1880260.htmlscala2.10.4Http://www.scala-lang.org/download/2.10.4.htmlScala for Eclipse plugin downloadSo I installed it through help->install new software. Add Input URL:The URL is connected from here (official website) to (:Http://scala-ide.org/download/prev-stable.htmlFor Scala 2.10.4Http://download.scala-ide.org/sdk/helium/e38/sca
Breezedensematrix, which is populated by the D1 element corresponding to the features corresponding position. -Val A2 =NewBDM (features.rows, Features.cols, D1) the ///:* means that each element is multiplied sequentially. Get Breezedensematrix. -Val features2 = Features:*A2 - ///Return (Breezedensematrix,breezedensematrix) constitutes the RDD. As a function return value, update addnoise. - (F._1, Features2) + } - ///Returns the result of the operation as a function return value. + addn
Transferred from: http://blog.csdn.net/huanbia/article/details/51318278Problem description
When using SECURECRT to open Spark-shell, sometimes the following problems, when the wrong time to press the BACKSPACE (BACKSPACE) or delete (delete key), you cannot delete the previously deleted content.
WorkaroundThe problem arises primarily in our securecrt, and we only need to change the emulation terminal in the session option to Linux.This can be cl
The definition of a type variable:The upper bound of the type variable, the lower bound of the type variable.The upper bound is the subclass of the type that must be defined, see the following example:Package com.dt.scala.type_parameterization//We need to define a generic class pair with a bigger method in the generic class that compares the arguments passed in//at which time the generic type must be a subclass of comparable. We can use Next: Type must be a parent of a defined typeWe use the: sy
file system, read the file from HDFs by default
classification and function of spark operators
value type transformation operator
input partition and output partition one-to- one
Map
FlatMap
mappartitions
Glom
input partition and output partition many-to-one type
Union
Cartesian
input partition and output partition Many-to-many types
GroupBy
output partition as input partition subset type
Filter
distinct
Subtract
Sample
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Random forest classifier:
Introduction to the algorithm:
Stochastic forest is an integrated algorithm of decision tree. Random forests contain multiple decision trees to reduce the risk of fitting. Stochastic forest has the characteristics of easy to explain, can deal with category, easy to expand to multiple classifications, and need not feature scaling.
Random forests train a series of decision trees separately, so the training process is parallel. By adding stochastic processes to the algorit
, 0.5, 0.5)
In fact, as with the slice parameter in Scala, the key is that the second parameter is until not To,slice (Start:int, Until:int)
Val subvector:densevector[double] = X.slice (2, 5);
println ("subvector:" + subvector);
/**
*
Vectorized-set Operator: = (: = is a to the quantization set operation)
* The
slice operator constructs a read-through and Write-through view of the given elements in the underlying
Or.
;=0).
Mininfogain:
Type: double-precision.
Meaning: The minimum information gain required to split a node.
Mininstancespernode:
Type: integer type.
Meaning: The minimum number of instances that are included in a node since splitting.
Predictioncol:
Type: String type.
Meaning: The forecast result column name.
Seed
Type: Long integral type.
Meaning: Random seeds.
Subsamplingrate:
Type: double-precision.
Meaning: Learn a decision tree using the training data scale, range [0,1].
Stepsize:
Type: doub
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