+ All Categories
Home > Documents > On R for Statisticsacmsc/SFD2011/subhajit_r.pdf · 2016-12-22 · On R for Statistics Subhajit...

On R for Statisticsacmsc/SFD2011/subhajit_r.pdf · 2016-12-22 · On R for Statistics Subhajit...

Date post: 23-Jun-2020
Category:
Upload: others
View: 2 times
Download: 0 times
Share this document with a friend
42
On R for Statistics Subhajit Dutta Stat-Math Unit Indian Statistical Institute, Kolkata September 16, 2011
Transcript
Page 1: On R for Statisticsacmsc/SFD2011/subhajit_r.pdf · 2016-12-22 · On R for Statistics Subhajit Dutta Stat-Math Unit Indian Statistical Institute, Kolkata September 16, 2011. ... and

On R for Statistics

Subhajit DuttaStat-Math Unit

Indian Statistical Institute, KolkataSeptember 16, 2011

Page 2: On R for Statisticsacmsc/SFD2011/subhajit_r.pdf · 2016-12-22 · On R for Statistics Subhajit Dutta Stat-Math Unit Indian Statistical Institute, Kolkata September 16, 2011. ... and

Why R ? – It is FREE !!

Basic as well as specialized data analysis technique atyour fingertips.Highly competitive with existing expensive statisticalpackages (like Matlab, SAS, SPSS).Very small installer file (∼ 30 MB).Easy to write codes.Draw on the talents of data scientists worldwide.

Page 3: On R for Statisticsacmsc/SFD2011/subhajit_r.pdf · 2016-12-22 · On R for Statistics Subhajit Dutta Stat-Math Unit Indian Statistical Institute, Kolkata September 16, 2011. ... and

History

S was developed by John Chambers and others at BellLabs, 1976 as an internal statistical analysis environment.

In 1993, Bell Labs gave Stat Sci (now Insightful Corp.) anexclusive license to develop, and sell the S language.

R was created by Ross Ihaka and Robert Gentleman atthe University of Auckland, New Zealand, in 1991.

In 1997, the R-Core Group was formed.

The first R version 1.0.0 is released in 2000.

Chambers is now a member of the R-Core Group.

R is named partly after the first names of the first two Rauthors, and partly as a play on the name of S.

Page 4: On R for Statisticsacmsc/SFD2011/subhajit_r.pdf · 2016-12-22 · On R for Statistics Subhajit Dutta Stat-Math Unit Indian Statistical Institute, Kolkata September 16, 2011. ... and

History

S was developed by John Chambers and others at BellLabs, 1976 as an internal statistical analysis environment.

In 1993, Bell Labs gave Stat Sci (now Insightful Corp.) anexclusive license to develop, and sell the S language.

R was created by Ross Ihaka and Robert Gentleman atthe University of Auckland, New Zealand, in 1991.

In 1997, the R-Core Group was formed.

The first R version 1.0.0 is released in 2000.

Chambers is now a member of the R-Core Group.

R is named partly after the first names of the first two Rauthors, and partly as a play on the name of S.

Page 5: On R for Statisticsacmsc/SFD2011/subhajit_r.pdf · 2016-12-22 · On R for Statistics Subhajit Dutta Stat-Math Unit Indian Statistical Institute, Kolkata September 16, 2011. ... and

History

S was developed by John Chambers and others at BellLabs, 1976 as an internal statistical analysis environment.

In 1993, Bell Labs gave Stat Sci (now Insightful Corp.) anexclusive license to develop, and sell the S language.

R was created by Ross Ihaka and Robert Gentleman atthe University of Auckland, New Zealand, in 1991.

In 1997, the R-Core Group was formed.

The first R version 1.0.0 is released in 2000.Chambers is now a member of the R-Core Group.

R is named partly after the first names of the first two Rauthors, and partly as a play on the name of S.

Page 6: On R for Statisticsacmsc/SFD2011/subhajit_r.pdf · 2016-12-22 · On R for Statistics Subhajit Dutta Stat-Math Unit Indian Statistical Institute, Kolkata September 16, 2011. ... and

History

S was developed by John Chambers and others at BellLabs, 1976 as an internal statistical analysis environment.

In 1993, Bell Labs gave Stat Sci (now Insightful Corp.) anexclusive license to develop, and sell the S language.

R was created by Ross Ihaka and Robert Gentleman atthe University of Auckland, New Zealand, in 1991.

In 1997, the R-Core Group was formed.

The first R version 1.0.0 is released in 2000.Chambers is now a member of the R-Core Group.

R is named partly after the first names of the first two Rauthors, and partly as a play on the name of S.

Page 7: On R for Statisticsacmsc/SFD2011/subhajit_r.pdf · 2016-12-22 · On R for Statistics Subhajit Dutta Stat-Math Unit Indian Statistical Institute, Kolkata September 16, 2011. ... and

The Developers

Page 8: On R for Statisticsacmsc/SFD2011/subhajit_r.pdf · 2016-12-22 · On R for Statistics Subhajit Dutta Stat-Math Unit Indian Statistical Institute, Kolkata September 16, 2011. ... and

The Developers

Page 9: On R for Statisticsacmsc/SFD2011/subhajit_r.pdf · 2016-12-22 · On R for Statistics Subhajit Dutta Stat-Math Unit Indian Statistical Institute, Kolkata September 16, 2011. ... and

Design of R

The R system is divided into 2 conceptual parts :

The base R system.User created packages : Allows specialized statisticaltechniques.

R functionality is divided into a number of packages, 4300(as of March 2011) are available.Download from Comprehensive R Archive Network(CRAN), which contains mirrors throughout the world.No mirrors in India, yet.

Page 10: On R for Statisticsacmsc/SFD2011/subhajit_r.pdf · 2016-12-22 · On R for Statistics Subhajit Dutta Stat-Math Unit Indian Statistical Institute, Kolkata September 16, 2011. ... and

Design of R

The R system is divided into 2 conceptual parts :The base R system.

User created packages : Allows specialized statisticaltechniques.

R functionality is divided into a number of packages, 4300(as of March 2011) are available.Download from Comprehensive R Archive Network(CRAN), which contains mirrors throughout the world.No mirrors in India, yet.

Page 11: On R for Statisticsacmsc/SFD2011/subhajit_r.pdf · 2016-12-22 · On R for Statistics Subhajit Dutta Stat-Math Unit Indian Statistical Institute, Kolkata September 16, 2011. ... and

Design of R

The R system is divided into 2 conceptual parts :The base R system.User created packages : Allows specialized statisticaltechniques.

R functionality is divided into a number of packages, 4300(as of March 2011) are available.Download from Comprehensive R Archive Network(CRAN), which contains mirrors throughout the world.No mirrors in India, yet.

Page 12: On R for Statisticsacmsc/SFD2011/subhajit_r.pdf · 2016-12-22 · On R for Statistics Subhajit Dutta Stat-Math Unit Indian Statistical Institute, Kolkata September 16, 2011. ... and

Design of R

The R system is divided into 2 conceptual parts :The base R system.User created packages : Allows specialized statisticaltechniques.

R functionality is divided into a number of packages, 4300(as of March 2011) are available.

Download from Comprehensive R Archive Network(CRAN), which contains mirrors throughout the world.No mirrors in India, yet.

Page 13: On R for Statisticsacmsc/SFD2011/subhajit_r.pdf · 2016-12-22 · On R for Statistics Subhajit Dutta Stat-Math Unit Indian Statistical Institute, Kolkata September 16, 2011. ... and

Design of R

The R system is divided into 2 conceptual parts :The base R system.User created packages : Allows specialized statisticaltechniques.

R functionality is divided into a number of packages, 4300(as of March 2011) are available.Download from Comprehensive R Archive Network(CRAN), which contains mirrors throughout the world.

No mirrors in India, yet.

Page 14: On R for Statisticsacmsc/SFD2011/subhajit_r.pdf · 2016-12-22 · On R for Statistics Subhajit Dutta Stat-Math Unit Indian Statistical Institute, Kolkata September 16, 2011. ... and

Design of R

The R system is divided into 2 conceptual parts :The base R system.User created packages : Allows specialized statisticaltechniques.

R functionality is divided into a number of packages, 4300(as of March 2011) are available.Download from Comprehensive R Archive Network(CRAN), which contains mirrors throughout the world.No mirrors in India, yet.

Page 15: On R for Statisticsacmsc/SFD2011/subhajit_r.pdf · 2016-12-22 · On R for Statistics Subhajit Dutta Stat-Math Unit Indian Statistical Institute, Kolkata September 16, 2011. ... and

Areas of application

Applications are listed at :

http://cran.r-project.org/web/views/

Statistical Pattern Recognition, Spatial and BayesianStatistics.Finance, Genetics, Machine Learning, Medical Imagingand Social Sciences.The Bioconductor (hosted by Fred Hutchinson CancerResearch Center, USA) project provides 460 R packages.Microarrays, High Throughput Assays, Sequence Data and Annotation.

Google uses R to make online advertising more effective.Statistics : The Secret Weapon of Successful Web Giants (JSM, 2011).

Page 16: On R for Statisticsacmsc/SFD2011/subhajit_r.pdf · 2016-12-22 · On R for Statistics Subhajit Dutta Stat-Math Unit Indian Statistical Institute, Kolkata September 16, 2011. ... and

Areas of application

Applications are listed at :

http://cran.r-project.org/web/views/

Statistical Pattern Recognition, Spatial and BayesianStatistics.

Finance, Genetics, Machine Learning, Medical Imagingand Social Sciences.The Bioconductor (hosted by Fred Hutchinson CancerResearch Center, USA) project provides 460 R packages.Microarrays, High Throughput Assays, Sequence Data and Annotation.

Google uses R to make online advertising more effective.Statistics : The Secret Weapon of Successful Web Giants (JSM, 2011).

Page 17: On R for Statisticsacmsc/SFD2011/subhajit_r.pdf · 2016-12-22 · On R for Statistics Subhajit Dutta Stat-Math Unit Indian Statistical Institute, Kolkata September 16, 2011. ... and

Areas of application

Applications are listed at :

http://cran.r-project.org/web/views/

Statistical Pattern Recognition, Spatial and BayesianStatistics.Finance, Genetics, Machine Learning, Medical Imagingand Social Sciences.

The Bioconductor (hosted by Fred Hutchinson CancerResearch Center, USA) project provides 460 R packages.Microarrays, High Throughput Assays, Sequence Data and Annotation.

Google uses R to make online advertising more effective.Statistics : The Secret Weapon of Successful Web Giants (JSM, 2011).

Page 18: On R for Statisticsacmsc/SFD2011/subhajit_r.pdf · 2016-12-22 · On R for Statistics Subhajit Dutta Stat-Math Unit Indian Statistical Institute, Kolkata September 16, 2011. ... and

Areas of application

Applications are listed at :

http://cran.r-project.org/web/views/

Statistical Pattern Recognition, Spatial and BayesianStatistics.Finance, Genetics, Machine Learning, Medical Imagingand Social Sciences.The Bioconductor (hosted by Fred Hutchinson CancerResearch Center, USA) project provides 460 R packages.Microarrays, High Throughput Assays, Sequence Data and Annotation.

Google uses R to make online advertising more effective.Statistics : The Secret Weapon of Successful Web Giants (JSM, 2011).

Page 19: On R for Statisticsacmsc/SFD2011/subhajit_r.pdf · 2016-12-22 · On R for Statistics Subhajit Dutta Stat-Math Unit Indian Statistical Institute, Kolkata September 16, 2011. ... and

Areas of application

Applications are listed at :

http://cran.r-project.org/web/views/

Statistical Pattern Recognition, Spatial and BayesianStatistics.Finance, Genetics, Machine Learning, Medical Imagingand Social Sciences.The Bioconductor (hosted by Fred Hutchinson CancerResearch Center, USA) project provides 460 R packages.Microarrays, High Throughput Assays, Sequence Data and Annotation.

Google uses R to make online advertising more effective.Statistics : The Secret Weapon of Successful Web Giants (JSM, 2011).

Page 20: On R for Statisticsacmsc/SFD2011/subhajit_r.pdf · 2016-12-22 · On R for Statistics Subhajit Dutta Stat-Math Unit Indian Statistical Institute, Kolkata September 16, 2011. ... and

Powerful and excellent Visualizations

Page 21: On R for Statisticsacmsc/SFD2011/subhajit_r.pdf · 2016-12-22 · On R for Statistics Subhajit Dutta Stat-Math Unit Indian Statistical Institute, Kolkata September 16, 2011. ... and

Powerful and excellent Visualizations

Page 22: On R for Statisticsacmsc/SFD2011/subhajit_r.pdf · 2016-12-22 · On R for Statistics Subhajit Dutta Stat-Math Unit Indian Statistical Institute, Kolkata September 16, 2011. ... and

Powerful and excellent Visualizations

Page 23: On R for Statisticsacmsc/SFD2011/subhajit_r.pdf · 2016-12-22 · On R for Statistics Subhajit Dutta Stat-Math Unit Indian Statistical Institute, Kolkata September 16, 2011. ... and

Powerful and excellent Visualizations

Page 24: On R for Statisticsacmsc/SFD2011/subhajit_r.pdf · 2016-12-22 · On R for Statistics Subhajit Dutta Stat-Math Unit Indian Statistical Institute, Kolkata September 16, 2011. ... and

Advantages of using R

A lot of packages are uploaded by the authors/theirstudents.

It contains advanced statistical routines not yet available inother softwares.Workspace can be saved, and shifted to another someother computer.Lines of script are significantly less, and hence easier fordebugging.Codes in C can be interfaced with R, and vice versa.Respects C, in the sense that it retains the speed of the Ccode when run in an R environment.R code/data written by you can be shared with the rest ofthe statistics community as a package.

Page 25: On R for Statisticsacmsc/SFD2011/subhajit_r.pdf · 2016-12-22 · On R for Statistics Subhajit Dutta Stat-Math Unit Indian Statistical Institute, Kolkata September 16, 2011. ... and

Advantages of using R

A lot of packages are uploaded by the authors/theirstudents.It contains advanced statistical routines not yet available inother softwares.

Workspace can be saved, and shifted to another someother computer.Lines of script are significantly less, and hence easier fordebugging.Codes in C can be interfaced with R, and vice versa.Respects C, in the sense that it retains the speed of the Ccode when run in an R environment.R code/data written by you can be shared with the rest ofthe statistics community as a package.

Page 26: On R for Statisticsacmsc/SFD2011/subhajit_r.pdf · 2016-12-22 · On R for Statistics Subhajit Dutta Stat-Math Unit Indian Statistical Institute, Kolkata September 16, 2011. ... and

Advantages of using R

A lot of packages are uploaded by the authors/theirstudents.It contains advanced statistical routines not yet available inother softwares.Workspace can be saved, and shifted to another someother computer.

Lines of script are significantly less, and hence easier fordebugging.Codes in C can be interfaced with R, and vice versa.Respects C, in the sense that it retains the speed of the Ccode when run in an R environment.R code/data written by you can be shared with the rest ofthe statistics community as a package.

Page 27: On R for Statisticsacmsc/SFD2011/subhajit_r.pdf · 2016-12-22 · On R for Statistics Subhajit Dutta Stat-Math Unit Indian Statistical Institute, Kolkata September 16, 2011. ... and

Advantages of using R

A lot of packages are uploaded by the authors/theirstudents.It contains advanced statistical routines not yet available inother softwares.Workspace can be saved, and shifted to another someother computer.Lines of script are significantly less, and hence easier fordebugging.

Codes in C can be interfaced with R, and vice versa.Respects C, in the sense that it retains the speed of the Ccode when run in an R environment.R code/data written by you can be shared with the rest ofthe statistics community as a package.

Page 28: On R for Statisticsacmsc/SFD2011/subhajit_r.pdf · 2016-12-22 · On R for Statistics Subhajit Dutta Stat-Math Unit Indian Statistical Institute, Kolkata September 16, 2011. ... and

Advantages of using R

A lot of packages are uploaded by the authors/theirstudents.It contains advanced statistical routines not yet available inother softwares.Workspace can be saved, and shifted to another someother computer.Lines of script are significantly less, and hence easier fordebugging.Codes in C can be interfaced with R, and vice versa.

Respects C, in the sense that it retains the speed of the Ccode when run in an R environment.R code/data written by you can be shared with the rest ofthe statistics community as a package.

Page 29: On R for Statisticsacmsc/SFD2011/subhajit_r.pdf · 2016-12-22 · On R for Statistics Subhajit Dutta Stat-Math Unit Indian Statistical Institute, Kolkata September 16, 2011. ... and

Advantages of using R

A lot of packages are uploaded by the authors/theirstudents.It contains advanced statistical routines not yet available inother softwares.Workspace can be saved, and shifted to another someother computer.Lines of script are significantly less, and hence easier fordebugging.Codes in C can be interfaced with R, and vice versa.Respects C, in the sense that it retains the speed of the Ccode when run in an R environment.

R code/data written by you can be shared with the rest ofthe statistics community as a package.

Page 30: On R for Statisticsacmsc/SFD2011/subhajit_r.pdf · 2016-12-22 · On R for Statistics Subhajit Dutta Stat-Math Unit Indian Statistical Institute, Kolkata September 16, 2011. ... and

Advantages of using R

A lot of packages are uploaded by the authors/theirstudents.It contains advanced statistical routines not yet available inother softwares.Workspace can be saved, and shifted to another someother computer.Lines of script are significantly less, and hence easier fordebugging.Codes in C can be interfaced with R, and vice versa.Respects C, in the sense that it retains the speed of the Ccode when run in an R environment.R code/data written by you can be shared with the rest ofthe statistics community as a package.

Page 31: On R for Statisticsacmsc/SFD2011/subhajit_r.pdf · 2016-12-22 · On R for Statistics Subhajit Dutta Stat-Math Unit Indian Statistical Institute, Kolkata September 16, 2011. ... and

Drawbacks, and comments from fellow users

Cannot handle huge data sets.

Usual R can easily handle 400 MB data.With the library ‘bigmemory’, there is no limit on data size.But, using it is not as easy for beginners, as usual R is.

Slow

Specific commands can improve speed a lot.

Comments

Support : send an e-mail to "[email protected]" and youwill get very good/fast response.Anything related to Math/Stat/Finance, you will get anexisting package/function.You have the scope to explore.

Page 32: On R for Statisticsacmsc/SFD2011/subhajit_r.pdf · 2016-12-22 · On R for Statistics Subhajit Dutta Stat-Math Unit Indian Statistical Institute, Kolkata September 16, 2011. ... and

Drawbacks, and comments from fellow users

Cannot handle huge data sets.Usual R can easily handle 400 MB data.

With the library ‘bigmemory’, there is no limit on data size.But, using it is not as easy for beginners, as usual R is.

Slow

Specific commands can improve speed a lot.

Comments

Support : send an e-mail to "[email protected]" and youwill get very good/fast response.Anything related to Math/Stat/Finance, you will get anexisting package/function.You have the scope to explore.

Page 33: On R for Statisticsacmsc/SFD2011/subhajit_r.pdf · 2016-12-22 · On R for Statistics Subhajit Dutta Stat-Math Unit Indian Statistical Institute, Kolkata September 16, 2011. ... and

Drawbacks, and comments from fellow users

Cannot handle huge data sets.Usual R can easily handle 400 MB data.With the library ‘bigmemory’, there is no limit on data size.But, using it is not as easy for beginners, as usual R is.

Slow

Specific commands can improve speed a lot.

Comments

Support : send an e-mail to "[email protected]" and youwill get very good/fast response.Anything related to Math/Stat/Finance, you will get anexisting package/function.You have the scope to explore.

Page 34: On R for Statisticsacmsc/SFD2011/subhajit_r.pdf · 2016-12-22 · On R for Statistics Subhajit Dutta Stat-Math Unit Indian Statistical Institute, Kolkata September 16, 2011. ... and

Drawbacks, and comments from fellow users

Cannot handle huge data sets.Usual R can easily handle 400 MB data.With the library ‘bigmemory’, there is no limit on data size.But, using it is not as easy for beginners, as usual R is.

Slow

Specific commands can improve speed a lot.

Comments

Support : send an e-mail to "[email protected]" and youwill get very good/fast response.Anything related to Math/Stat/Finance, you will get anexisting package/function.You have the scope to explore.

Page 35: On R for Statisticsacmsc/SFD2011/subhajit_r.pdf · 2016-12-22 · On R for Statistics Subhajit Dutta Stat-Math Unit Indian Statistical Institute, Kolkata September 16, 2011. ... and

Drawbacks, and comments from fellow users

Cannot handle huge data sets.Usual R can easily handle 400 MB data.With the library ‘bigmemory’, there is no limit on data size.But, using it is not as easy for beginners, as usual R is.

SlowSpecific commands can improve speed a lot.

Comments

Support : send an e-mail to "[email protected]" and youwill get very good/fast response.Anything related to Math/Stat/Finance, you will get anexisting package/function.You have the scope to explore.

Page 36: On R for Statisticsacmsc/SFD2011/subhajit_r.pdf · 2016-12-22 · On R for Statistics Subhajit Dutta Stat-Math Unit Indian Statistical Institute, Kolkata September 16, 2011. ... and

Drawbacks, and comments from fellow users

Cannot handle huge data sets.Usual R can easily handle 400 MB data.With the library ‘bigmemory’, there is no limit on data size.But, using it is not as easy for beginners, as usual R is.

SlowSpecific commands can improve speed a lot.

Comments

Support : send an e-mail to "[email protected]" and youwill get very good/fast response.Anything related to Math/Stat/Finance, you will get anexisting package/function.You have the scope to explore.

Page 37: On R for Statisticsacmsc/SFD2011/subhajit_r.pdf · 2016-12-22 · On R for Statistics Subhajit Dutta Stat-Math Unit Indian Statistical Institute, Kolkata September 16, 2011. ... and

Drawbacks, and comments from fellow users

Cannot handle huge data sets.Usual R can easily handle 400 MB data.With the library ‘bigmemory’, there is no limit on data size.But, using it is not as easy for beginners, as usual R is.

SlowSpecific commands can improve speed a lot.

CommentsSupport : send an e-mail to "[email protected]" and youwill get very good/fast response.

Anything related to Math/Stat/Finance, you will get anexisting package/function.You have the scope to explore.

Page 38: On R for Statisticsacmsc/SFD2011/subhajit_r.pdf · 2016-12-22 · On R for Statistics Subhajit Dutta Stat-Math Unit Indian Statistical Institute, Kolkata September 16, 2011. ... and

Drawbacks, and comments from fellow users

Cannot handle huge data sets.Usual R can easily handle 400 MB data.With the library ‘bigmemory’, there is no limit on data size.But, using it is not as easy for beginners, as usual R is.

SlowSpecific commands can improve speed a lot.

CommentsSupport : send an e-mail to "[email protected]" and youwill get very good/fast response.Anything related to Math/Stat/Finance, you will get anexisting package/function.

You have the scope to explore.

Page 39: On R for Statisticsacmsc/SFD2011/subhajit_r.pdf · 2016-12-22 · On R for Statistics Subhajit Dutta Stat-Math Unit Indian Statistical Institute, Kolkata September 16, 2011. ... and

Drawbacks, and comments from fellow users

Cannot handle huge data sets.Usual R can easily handle 400 MB data.With the library ‘bigmemory’, there is no limit on data size.But, using it is not as easy for beginners, as usual R is.

SlowSpecific commands can improve speed a lot.

CommentsSupport : send an e-mail to "[email protected]" and youwill get very good/fast response.Anything related to Math/Stat/Finance, you will get anexisting package/function.You have the scope to explore.

Page 40: On R for Statisticsacmsc/SFD2011/subhajit_r.pdf · 2016-12-22 · On R for Statistics Subhajit Dutta Stat-Math Unit Indian Statistical Institute, Kolkata September 16, 2011. ... and

“The best thing about R is that it was developed by statisticians.The worst thing about R is that.....

it was developed by statisticians.” – Bo Cowgill, Google.

R you ready for R ?

Thanks to Buddha, Dibyendu Da, Palash Da, Utkarsh and of course, Google.

Page 41: On R for Statisticsacmsc/SFD2011/subhajit_r.pdf · 2016-12-22 · On R for Statistics Subhajit Dutta Stat-Math Unit Indian Statistical Institute, Kolkata September 16, 2011. ... and

“The best thing about R is that it was developed by statisticians.The worst thing about R is that.....

it was developed by statisticians.” – Bo Cowgill, Google.

R you ready for R ?

Thanks to Buddha, Dibyendu Da, Palash Da, Utkarsh and of course, Google.

Page 42: On R for Statisticsacmsc/SFD2011/subhajit_r.pdf · 2016-12-22 · On R for Statistics Subhajit Dutta Stat-Math Unit Indian Statistical Institute, Kolkata September 16, 2011. ... and

“The best thing about R is that it was developed by statisticians.The worst thing about R is that.....

it was developed by statisticians.” – Bo Cowgill, Google.

R you ready for R ?

Thanks to Buddha, Dibyendu Da, Palash Da, Utkarsh and of course, Google.


Recommended