When working with big data with R (say, using Spark and sparklyr) we have found it very convenient to keep data handles in a neat list ordata_frame. Please read on for our handy hints on keeping your data handles neat. When using R to work over a big…

7 Tools for Data Visualization in R, Python, and Julia Last week, some examples of creating visualizations with htmlwidgets and R were presented. Fortunately, there are many more options available for creating nice visualizations. Tools and libraries…

Managing Hierarchical Data in MySQL Introduction Most users at one time or another have dealt with hierarchical data in a SQL database and no doubt learned that the management of hierarchical data is not what a relational database is intended for. Th…

Around September of 2016 I wrote two articles on using Python for accessing, visualizing, and evaluating trading strategies (see part 1 and part 2). These have been my most popular posts, up until I published my article on learning programming langua…

dplyr and data.table are amazing packages that make data manipulation in R fun. Both packages have their strengths. While dplyr is more elegant and resembles natural language, data.table is succinct and we can do a lot withdata.table in just a single…

use this val data = sc.textFile("/home/spark/data.txt") this should work and set master as local. Input path does not exist解决方法 spark-submit --master local 即可解决! 参考:https://stackoverflow.com/questions/41339127/how-to-load-local-file-using-sc-tex…

R Projects Similar to Python, when we installed the data science tools we get an “R” section in our templates. If you go there you’ll see something like this: Only one template to choose from, but that’s ok! That is all we need. R Interactive Just li…

原文:http://mikehillyer.com/articles/managing-hierarchical-data-in-mysql/ 引言 大多数用户都曾在数据库中处理过分层数据(hierarchical data),认为分层数据的管理不是关系数据库的目的.之所以这么认为,是因为关系数据库中的表没有层次关系,只是简单的平面化的列表:而分层数据具有父-子关系,显然关系数据库中的表不能自然地表现出其分层的特性. 我们认为,分层数据是每项只有一个父项和零个或多个子项(根项除外,根项没有父项)…

原文在:http://dev.mysql.com/tech-resources/articles/hierarchical-data.html 来源: http://www.cnblogs.com/phaibin/archive/2009/06/09/1499687.html 译文:Yimin 引言 大多数用户都曾在数据库中处理过分层数据(hierarchical data),认为分层数据的管理不是关系数据库的目的.之所以这么认为,是因为关系数据库中的表没有层次关系,只是简单的平面化的列表:而分…

1.代码 import java.io.Serializable; import java.util.NavigableMap; import java.util.Random; import java.util.TreeMap; public class Zifp_gen implements Serializable { ); NavigableMap<Double, Integer> map; private static final double Constant = 1.0; pub…