# Colored Histogram with Different Number of Bins
hist(mtcars$mpg, breaks=12, col="red")
click to view
# Add a Normal Curve (Thanks to Peter Dalgaard)
x <- mtcars$mpg
h<-hist(x, breaks=10, col="red", xlab="Miles Per Gallon",
main="Histogram with Normal Curve")
xfit<-seq(min(x),max(x),length=40)
yfit<-dnorm(xfit,mean=mean(x),sd=sd(x))
yfit <- yfit*diff(h$mids[1:2])*length(x)
lines(xfit, yfit, col="blue", lwd=2)
click to view
Histograms can be a poor method for determining the shape of a distribution because it is so strongly affected by the number of bins used.
KERNEL DENSITY PLOTS
Kernal density plots are usually a much more effective way to view the distribution of a variable. Create the plot using plot(density(x)) where x is a numeric vector.
# Kernel Density Plot
d <- density(mtcars$mpg) # returns the density data
plot(d) # plots the results
click to view
# Filled Density Plot
d <- density(mtcars$mpg)
plot(d, main="Kernel Density of Miles Per Gallon")
polygon(d, col="red", border="blue")
click to view
COMPARING GROUPS VIA KERNAL DENSITY
The sm.density.compare( ) function in the smpackage allows you to superimpose the kernal density plots of two or more groups. The format is sm.density.compare(x, factor) where x is a numeric vector and factor is the grouping variable.
# Compare MPG distributions for cars with
# 4,6, or 8 cylinders
library(sm)
attach(mtcars)
I have received numerous requests for a hardcopy version of this site, so over the past year I have been writing a book that takes the material here and significantly expands upon it. If you are interested, early access is available.
If you have not been to that website, I recommend it highly (though the tagline or logo of R for SAS/SPSS/Stata users seems a bit familiar)-http://www.statmethods.net/index.html
Over the month long break I took, I was helping firm up my ideas for R for Analytics , I also took a break and read some books. Here are brief reviews of two, three of them-
1) Hindu Myths
This is a classical book translated from original Sanskrit written by Professor Wendy O Flaherty of University of Chicago. I found some of the older myths very interesting in terms of contradictions, retelling the same story in a modified way by another classic, the beautiful poetic and fantastic imagery evoked by Hindu myths. Some stories are as relevant in prayers, fasts and religious ceremonies as they were around 11000 years while most have morphed , edited or even distorted.
It should help the non Indian reader understand why hundreds of millions of conservative Indians worship Shiv Ling ( or literally an idol of the Phallus of Shiva), the Hindu two cents of creation of the universe, and the somewhat fantastic stories on super heroes /gods/ in the ancient world.
The book suffers from a few drawbacks in my opinion-
1) Sanskrit is a bit like Latin- you can lose not just the flavor but original meaning of words and situational context. Some of the stories made better sense when i read a more recent Hindi translation.
2) An excessive emphasis on sexual imagery rather than emotional imagery. The author seems wonder struck to read and translate ancient indians were so matter of fact about physical relationships. However the words were always written in discrete poetic than crass soft pornography.
3) Almost no drawings or figures. This makes the book a bit dense to read at 300 pages.
I liked another book on Hindu Myths (Myth= Mithya which I read in 2009) and you can see if you can read it if you find the topic interesting.
A Handbook of Hindu Mythology
Hindus have one God.
They also have 330 million gods: male gods, female gods, personal gods, family gods, household gods, village gods, gods of space and time, gods for specific castes and particular professions, gods who reside in trees, in animals, in minerals, in geometrical patterns and in man-made objects.
Then there are a whole host of demons.
But no Devil.
Mere Christianity by C S Lewis is a classic book on reinterpreting Christianity in modern times. However the author wrote this when World War 2 was on and it seems more like a British or Anglo Saxon interpretation of beliefs of Christ Jesus– who was actually a Jewish teacher born in Middle East Asia.
While the language and reading makes it much easier to read- it is recommended more at Western audiences, than Eastern ones, as it seems some of the parables are a more palatable re interpretation of the New Testament. The Bible is a deceptively easy book to read, the language is short and beautiful-and the original parables in the Gospels remain powerful easy to understand.
C S Lewis tends to emphasize morality than religiosity or faith, and there is not much comparison with any other faith or alternative morality. Dumbing down the Bible so as to market it better to reluctant consumers seems to be Mr Lewis intention and it is not as scholarly a work as an exercise in pure prose.
However it is quite good as a self improvement book and is quite better than the “You Can Win” kind of books or even business concept books.
Note- I find reading books on religion as good exercises in reading the fountain source of philosophies. As a polytheist- I tend to read more than one faith.
The only issue is Rattle can be quite difficult to install due to dependencies on GTK+
After fiddling for a couple of years- this is what I did
1) Created dual boot OS- Basically downloaded the netbook remix from http://ubuntu.com I created a dual boot OS so you can choose at the beginning whether to use Windows or Ubuntu Linux in that session. Alternatively you can download VM Player www.vmware.com/products/player/ if you want to do both
2) Download R packages using Ubuntu packages and Install GTK+ dependencies before that.
GTK + Requires
Libglade
Glib
Cairo
Pango
ATK
If you are a Linux newbie like me who doesnt get the sudo apt get, tar, cd, make , install rigmarole – scoot over to synaptic software packages or just the main ubuntu software centre and download these packages one by one.
For R Dependencies, you need
PMML
XML
RGTK2
Again use r-cran as the prefix to these package names and simply install (almost the same way Windows does it easily -double click)
Save theses to your hard disk (e.g., to your Desktop) but don’t extract them. Then, on GNU/Linux run the install command shown below. This command is entered into a terminal window:
R CMD INSTALL rattle_2.6.0.tar.gz
After installation-
5) Type library(rattle) and rattle.info to get messages on what R packages to update for a proper functioning
</code>
> library(rattle)
Rattle: Graphical interface for data mining using R.
Version 2.6.0 Copyright (c) 2006-2010 Togaware Pty Ltd.
Type 'rattle()' to shake, rattle, and roll your data.
> rattle.info()
Rattle: version 2.6.0
R: version 2.11.1 (2010-05-31) (Revision 52157)
Sysname: Linux
Release: 2.6.35-23-generic
Version: #41-Ubuntu SMP Wed Nov 24 10:18:49 UTC 2010
Nodename: k1-M725R
Machine: i686
Login: k1ng
User: k1ng
Installed Dependencies
RGtk2: version 2.20.3
pmml: version 1.2.26
colorspace: version 1.0-1
cairoDevice: version 2.14
doBy: version 4.1.2
e1071: version 1.5-24
ellipse: version 0.3-5
foreign: version 0.8-41
gdata: version 2.8.1
gtools: version 2.6.2
gplots: version 2.8.0
gWidgetsRGtk2: version 0.0-69
Hmisc: version 3.8-3
kernlab: version 0.9-12
latticist: version 0.9-43
Matrix: version 0.999375-46
mice: version 2.4
network: version 1.5-1
nnet: version 7.3-1
party: version 0.9-99991
playwith: version 0.9-53
randomForest: version 4.5-36 upgrade available 4.6-2
rggobi: version 2.1.16
survival: version 2.36-2
XML: version 3.2-0
bitops: version 1.0-4.1
Upgrade the packages with:
> install.packages(c("randomForest"))
<code>
Now upgrade whatever package rattle.info tells to upgrade.
This is much simpler and less frustrating than some of the other ways to install Rattle.
If all goes well, you will see this familiar screen popup when you type
Additional features in R over other analytical packages-
1) Source Code is given to ensure complete custom solution and embedding for a particular application. Open source code has an advantage that is extensively peer- reviewed in Journals and Scientific Literature. This means bugs will found, shared and corrected transparently.
2) Wide literature of training material in the form of books is available for the R analytical platform.
3) Extensively the best data visualization tools in analytical software (apart from Tableau Software ‘s latest version). The extensive data visualization available in R is of the form a variety of customizable graphs, as well as animation. The principal reason third-party software initially started creating interfaces to R is because the graphical library of packages in R is more advanced as well as rapidly getting more features by the day.
4) Free in upfront license cost for academics and thus budget friendly for small and large analytical teams.
5) Flexible programming for your data environment. This includes having packages that ensure compatibility with Java, Python and C++.
6) Easy migration from other analytical platforms to R Platform. It is relatively easy for a non R platform user to migrate to R platform and there is no danger of vendor lock-in due to the GPL nature of source code and open community.
Statistics are numbers that tell (descriptive), advise ( prescriptive) or forecast (predictive). Analytics is a decision-making help tool. Analytics on which no decision is to be made or is being considered can be classified as purely statistical and non analytical. Thus ease of making a correct decision separates a good analytical platform from a not so good analytical platform. The distinction is likely to be disputed by people of either background- and business analysis requires more emphasis on how practical or actionable the results are and less emphasis on the statistical metrics in a particular data analysis task. I believe one clear reason between business analytics is different from statistical analysis is the cost of perfect information (data costs in real world) and the opportunity cost of delayed and distorted decision-making.
Specific to the following domains R has the following costs and benefits
Business Analytics
R is free per license and for download
It is one of the few analytical platforms that work on Mac OS
It’s results are credibly established in both journals like Journal of Statistical Software and in the work at LinkedIn, Google and Facebook’s analytical teams.
It has open source code for customization as per GPL
It also has a flexible option for commercial vendors like Revolution Analytics (who support 64 bit windows) as well as bigger datasets
It has interfaces from almost all other analytical software including SAS,SPSS, JMP, Oracle Data Mining, Rapid Miner. Existing license holders can thus invoke and use R from within these software
Huge library of packages for regression, time series, finance and modeling
High quality data visualization packages
Data Mining
R as a computing platform is better suited to the needs of data mining as it has a vast array of packages covering standard regression, decision trees, association rules, cluster analysis, machine learning, neural networks as well as exotic specialized algorithms like those based on chaos models.
Flexibility in tweaking a standard algorithm by seeing the source code
The RATTLE GUI remains the standard GUI for Data Miners using R. It was created and developed in Australia.
Business Dashboards and Reporting
Business Dashboards and Reporting are an essential piece of Business Intelligence and Decision making systems in organizations. R offers data visualization through GGPLOT, and GUI like Deducer and Red-R can help even non R users create a metrics dashboard
For online Dashboards- R has packages like RWeb, RServe and R Apache- which in combination with data visualization packages offer powerful dashboard capabilities.
R can be combined with MS Excel using the R Excel package – to enable R capabilities to be imported within Excel. Thus a MS Excel user with no knowledge of R can use the GUI within the R Excel plug-in to use powerful graphical and statistical capabilities.
Additional factors to consider in your R installation-
There are some more choices awaiting you now-
1) Licensing Choices-Academic Version or Free Version or Enterprise Version of R
2) Operating System Choices-Which Operating System to choose from? Unix, Windows or Mac OS.
3) Operating system sub choice- 32- bit or 64 bit.
4) Hardware choices-Cost -benefit trade-offs for additional hardware for R. Choices between local ,cluster and cloud computing.
5) Interface choices-Command Line versus GUI? Which GUI to choose as the default start-up option?
6) Software component choice- Which packages to install? There are almost 3000 packages, some of them are complimentary, some are dependent on each other, and almost all are free.
7) Additional Software choices- Which additional software do you need to achieve maximum accuracy, robustness and speed of computing- and how to use existing legacy software and hardware for best complementary results with R.
1) Licensing Choices-
You can choose between two kinds of R installations – one is free and open source from http://r-project.org The other R installation is commercial and is offered by many vendors including Revolution Analytics. However there are other commercial vendors too.
Windows remains the most widely used operating system on this planet. If you are experienced in Windows based computing and are active on analytical projects- it would not make sense for you to move to other operating systems. This is also based on the fact that compatibility problems are minimum for Microsoft Windows and the help is extensively documented. However there may be some R packages that would not function well under Windows- if that happens a multiple operating system is your next option.
Enterprise R from Revolution Analytics- Enterprise R from Revolution Analytics has a complete R Development environment for Windows including the use of code snippets to make programming faster. Revolution is also expected to make a GUI available by 2011. Revolution Analytics claims several enhancements for it’s version of R including the use of optimized libraries for faster performance.
MacOS
Reasons for choosing MacOS remains its considerable appeal in aesthetically designed software- but MacOS is not a standard Operating system for enterprise systems as well as statistical computing. However open source R claims to be quite optimized and it can be used for existing Mac users. However there seem to be no commercially available versions of R available as of now for this operating system.
Linux
Ubuntu
Red Hat Enterprise Linux
Other versions of Linux
Linux is considered a preferred operating system by R users due to it having the same open source credentials-much better fit for all R packages and it’s customizability for big data analytics.
Ubuntu Linux is recommended for people making the transition to Linux for the first time. Ubuntu Linux had an marketing agreement with revolution Analytics for an earlier version of Ubuntu- and many R packages can installed in a straightforward way as Ubuntu/Debian packages are available. Red Hat Enterprise Linux is officially supported by Revolution Analytics for it’s enterprise module. Other versions of Linux popular are Open SUSE.
Multiple operating systems-
Virtualization vs Dual Boot-
You can also choose between having a VMware VM Player for a virtual partition on your computers that is dedicated to R based computing or having operating system choice at the startup or booting of your computer. A software program called wubi helps with the dual installation of Linux and Windows.
64 bit vs 32 bit – Given a choice between 32 bit versus 64 bit versions of the same operating system like Linux Ubuntu, the 64 bit version would speed up processing by an approximate factor of 2. However you need to check whether your current hardware can support 64 bit operating systems and if so- you may want to ask your Information Technology manager to upgrade atleast some operating systems in your analytics work environment to 64 bit operating systems.
Hardware choices- At the time of writing this book, the dominant computing paradigm is workstation computing followed by server-client computing. However with the introduction of cloud computing, netbooks, tablet PCs, hardware choices are much more flexible in 2011 than just a couple of years back.
Hardware costs are a significant cost to an analytics environment and are also remarkably depreciated over a short period of time. You may thus examine your legacy hardware, and your future analytical computing needs- and accordingly decide between the various hardware options available for R.
Unlike other analytical software which can charge by number of processors, or server pricing being higher than workstation pricing and grid computing pricing extremely high if available- R is well suited for all kinds of hardware environment with flexible costs. Given the fact that R is memory intensive (it limits the size of data analyzed to the RAM size of the machine unless special formats and /or chunking is used)- it depends on size of datasets used and number of concurrent users analyzing the dataset. Thus the defining issue is not R but size of the data being analyzed.
Local Computing- This is meant to denote when the software is installed locally. For big data the data to be analyzed would be stored in the form of databases.
Server version- Revolution Analytics has differential pricing for server -client versions but for the open source version it is free and the same for Server or Workstation versions.
Workstation
Cloud Computing- Cloud computing is defined as the delivery of data, processing, systems via remote computers. It is similar to server-client computing but the remote server (also called cloud) has flexible computing in terms of number of processors, memory, and data storage. Cloud computing in the form of public cloud enables people to do analytical tasks on massive datasets without investing in permanent hardware or software as most public clouds are priced on pay per usage. The biggest cloud computing provider is Amazon and many other vendors provide services on top of it. Google is also coming for data storage in the form of clouds (Google Storage), as well as using machine learning in the form of API (Google Prediction API)
Amazon
Google
Cluster-Grid Computing/Parallel processing- In order to build a cluster, you would need the RMpi and the SNOW packages, among other packages that help with parallel processing.
How much resources
RAM-Hard Disk-Processors- for workstation computing
Instances or API calls for cloud computing
Interface Choices
Command Line
GUI
Web Interfaces
Software Component Choices
R dependencies
Packages to install
Recommended Packages
Additional software choices
Additional legacy software
Optimizing your R based computing
Code Editors
Code Analyzers
Libraries to speed up R
citation- R Development Core Team (2010). R: A language and environment for statistical computing. R Foundation for Statistical Computing,Vienna, Austria. ISBN 3-900051-07-0, URL http://www.R-project.org.
Tal G, creator of the rbloggers.com website, has created a new blog aggregator for SAS language users at http://sas-x.com/
With almost 26 blogs joining there (I suspect many more should join , it seems like a good website to use for analytics users and students. My favorite SAS Blog is http://statcompute.spaces.live.com/ – its pure code- little anything else.
and followed it up with how HE analyzed the post announcing the non-analysis.
“If you have not visited the site in a week or so you will have missed my previous post on analyzing WikiLeaks data, which from the traffic and 35 Comments and 255 Reactions was at least somewhat controversial. Given this rare spotlight I thought it would be fun to use the infochimps API to map out the geo-location of everyone that visited the blog post over the last few days. Unfortunately, after nearly two years with the same web hosting service, only today did I realize that I was not capturing daily log files for my domain”
Anyways – non American users of R Project can analyze the Wikileaks data using the R SPARQL package I would advise American friends not to use this approach or attempt to analyze any data because technically the data is still classified and it’s possession is illegal (which is the reason Federal employees and organizations receiving federal funds have advised not to use this or any WikiLeaks dataset)
In May 2009, the Obama administration started putting raw
government data on the Web.
It started with 47 data sets. Today, there are more than
270,000 government data sets, spanning every imaginable
category from public health to foreign aid.
in the middle of essential and inevitable tasks restless inner conscience wakens and asks stuck again today to the computer are we now please remind me this state we reached how
oh we had bills to pay student loans to repay once we got hooked t’was easy to be carried away just a matter of time before inevitable voices query this is my machine that I want to marry
I spend more time with him/her as it is the Machinery is devoted with focused loyalties meanwhile the non machine world goes round strives forth on things less profound
as we stroke the keys and click the mouse machine addictions will only add to human grouse
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DECISION STATS 