View source for R/C2/Introduction-to-Data-Frames-in-R/English-timed



{|Border=1
!Time
!Narration
|-
||0:00
||Welcome to the spoken tutorial on introduction to '''data frames''' in '''R'''.

|-
||00:05
||I am Kannan Moudgalya.

|-
||00:07
||In this tutorial, we will explain 

|-
||00:10
||how to create a '''data frame''' in '''R'''

|-
||00:13
||how to work with it

|-
||00:15
||how to save it into a file and

|-
||00:17
||how to read data from a file into a '''data frame'''

|-
||00:21
||We will also learn about the '''data sets''' that come with the '''R''' software

|-
||00:27
||To understand this tutorial,

|-
||00:29
||One needs to know elementary maths

|-
||00:32
||''for example, the meaning of mean, row and column''

|-
||00:35
||One needs to know how to edit a text file and plotting
|-
||00:39
||No programming background is required, however

|-
||00:42
||Anyone with a simple exposure to '''statistics''' can understand this tutorial

|-
||00:46
||Please locate this tutorial on our web page, '''spoken hyphen tutorial dot org'''

|-
||00:53
||Prerequisite spoken tutorials, if any, will be mentioned in this page

|-
||00:57
||I am using version '''3''' of '''R'''
'''RStudio 0.97'''
and '''Mac OS X 10.7'''

|-
||01:05
||But it should work in other versions and also other operating systems.

|-
||01:12
||Let us switch to '''Rstudio'''.

|-
||01:14
||Let us begin with the '''“c” command''' to create a '''vector'''

|-
||01:23
||Notice that I am using the '''assignment operator''', that is, '''less than''' followed by '''hyphen'''.

|-
||01:31
||I will use the word '''get''' to denote this '''assignment'''.

|-
||01:35
||This is the way to create a '''vector''' of three '''elements'''.

|-
||01:38
||'''c''' stands for '''create''' or '''concatenate'''.

|-
||01:42
||Although the '''equal to''' sign works most of the time, one usually uses this '''operator''' in '''R'''.

|-
||01:49
||Let us view what the '''vector sample '''contains.

|-
||01:56
||Let us now build a '''data set'''.

|-
||01:58
||We will also call it as a '''data frame''' in this tutorial.

|-
||02:03
||Let me create a '''vector''' of Indian Cricket Captains, old and new.

|-
||02:10
||'''names gets c of Mahi, Sourav, Azhar, Sunny, Pataudi, Dravid'''

|-
||02:46
||Each name has to be entered in between '''double quotes'''.

|-
||02:50
||Let us view what the variable '''names '''contains.

|-
||02:57
||I will create a '''vector''' to store the number of matches they captained.

|-
||03:15
||One can see that all the '''variables''' got entered in the '''workspace.''' 

|-
||03:21
||Now, let us put these together and create a '''data frame''' as I do now.

|-
||03:44
||It is '''data dot frame'''.

|-
||03:50
||Let us understand what the command '''data frame '''does.

|-
||03:55
||To do this, let us '''View brackets captaincy'''.

|-
||04:02
||The contents of the '''data frame''' appear nicely in the window above.

|-
||04:09
||What will happen if you just type '''captaincy''', without the '''View command'''?

|-
||04:14
||Would you want to try it now?

|-
||04:16
||In '''statistics''', one works with such '''data sets'''.

|-
||04:19
||Remember, the '''commands''' and '''variables''' in '''R''' are case sensitive.

|-
||04:24
||The '''View command''' begins with a '''capital V'''.

|-
||04:29
||It is easy to access the parts of a '''data frame'''.

|-
||04:32
||For example, this is how I will get the names in the '''captaincy data frame'''.

|-
||04:39
||Let us similarly get the number of matches won.

|-
||04:45
||Let us find the ratio of matches won.

|-
||04:54
||When we divide a '''vector''' by another, '''R''' carries out component-wise division.

|-
||04:59
||Let us include this ratio also in the '''captaincy data frame'''.

|-
||05:04
||'''captaincy dollar victory''' gets '''ratio'''.

|-
||05:13
||What is in '''ratio''' gets transferred to '''victory''', a variable in the '''data frame captaincy'''.

|-
||05:19
||We can check that ratio is included in captaincy by the '''View command'''.

|-
||05:26
||We can see that the '''ratio''' is included in victory.

|-
||05:31
||Let us reduce the number of digits displayed in the ratio to 2.

|-
||05:35
||We do this with the '''command options within brackets digits=2'''.

|-
||05:48
||Let us view '''captaincy.''

|-
||05:51
||We can see that it has been reduced to two digits.

|-
||05:56
||Let us see the number of matches played by all the captains.

|-
||06:03
||Let us find the '''mean''' of these matches.

|-
||06:07
||By direct calculation, we find that '''mean''' does exactly what it should.

|-
||06:16
||These two are equal.

|-
||06:18
||Let us now get some plots with this '''data frame'''.

|-
||06:22
||Let us plot the ratio of victories vs. the year of captaincy.

|-
||06:32
||Remember that the '''x''' axis variable has to be listed first in the '''plot''' command.

|-
||06:40
||Let us plot the number of matches captained versus the names of the captains.

|-
||06:50
||Drag this a little bit. The graph expands. Put it back.

|-
||06:58
||We will now explain how to write this '''data fram'''e to a '''comma separated variable''' file or '''C S       
  V'''.

|-
||07:06
||We will use the command '''write.csv''', as we do now.

|-
||07:15
||Let me move this to the right. 

|-
||07:23
||This writes the '''captaincy data frame''' into the file '''NewCaptaincy.csv'''

|-
||07:29
||Let me open this file using my favourite text editor, '''emacs'''.

|-
||07:34
||You may use any other text editor, such as '''notepad''' or '''vi''' or '''gedit'''.

|-
||07:40
||Please do not, however, use '''Microsoft office''' or '''LibreOffice Writer''' for this purpose.

|-
||07:46
||Because, you may not be able to load these files into '''R'''.

|-
||07:50
||Let us now see what the file '''NewCaptaincy.csv''' contains.
|-
||07:56
||This '''csv''' file contains everything that we created.

|-
||08:00
||It also contains row numbers in every row, at the beginning.

|-
||08:06
||How will you get rid of these row numbers?

|-
||08:09
||Add an additional flag called '''row dot names equals FALSE'''.

|-
||08:32
||Let us read the new version of this file in emacs.

|-
||08:40
||In '''emacs''', I just have to refresh it.

|-
||08:46
||In other editors, you may have to re-open the file.

|-
||08:50
||We see that the row numbers no longer appear.

|-
||08:53
||Let us make a small change in this '''csv''' file and read it.

|-
||08:57
||Let us change '''Mahi''' to '''Dhoni''' and save the file.

|-
||09:09
||Let us click '''Import Dataset'''.

|-
||09:19
||There are two options:

|-
||09:21
||from the text file and from the web.
 
|-
||09:25
||Reading from a local file is a fool-proof method.

|-
||09:28
||It works even if '''Internet''' is not available. 

|-
||09:31
||All one has to do is to download the required files ahead of time.

|-
||09:36
||Let us click the '''File''' option.

|-
||09:40
||Let us select '''NewCaptaincy.'''

|-
||09:47
||In order to see this, let's maximise this, let's '''Import''' this, let manimise this.

|-
||09:57
||You will not have this problem, of course, because, you will be using the whole screen.

|-
||10:03
||For this tutorial, I am using only a small portion of the screen.

|-
||10:08
||And that’s why we have had this problem.

|-
||10:11
||The appearance of a data frame called '''NewCaptaincy''' here, and also here, shows that it has been          read.

|-
||10:20
||It also has '''Dhoni''' as the name.

|-
||10:23
||The row numbers have also disappeared.
|-
||10:26
||It is also possible to read '''excel '''and '''ods''' files into '''R'''.
 
|-
||10:31
||This involves a little more work and hence not covered in this tutorial.

|-
||10:35
||It is easy to export '''excel''' and '''ods''' files into '''csv''' format.

|-
||10:40
||So, for now, please use the '''csv''' route to import '''excel''' or '''ods''' files.

|-
||10:47
||Let us take up the final topic for this tutorial.

|-
||10:50
||'''R''' comes with several '''data frames'''.

|-
||10:54
||To access them, issue the command '''data brackets'''.

|-
||11:03
||'''R''' shows a list of available '''data frames'''.

|-
||11:07
||We can carry out all sorts of calculations on these '''data sets'''.

|-
||11:12
||We will just view one '''data set''', called '''C O 2'''.

|-
||11:18
||We will conclude this tutorial here.

|-
||11:20
||In this tutorial, we learnt the following:

|-
||11:23
|| We created '''vectors'''

|-
||11:25
||We put the '''vectors''' into a '''data frame'''

|-
||11:27
||We operated on the '''data frame'''

|-
||11:29
||We saved the '''data frame''' into a file

|-
||11:32
||Imported the file into '''R'''

|-
||11:34
||Examined the '''data frames''' that came with '''R'''

|-
||11:38
||We now suggest an assignment.

|-
||11:40
||Find out how to calculate '''median''' using the '''help''' button.

|-
||11:48
||Repeat the above using web search.

|-
||11:51
||Calculate the '''mean''' and '''median''' of the '''data frame C O 2'''.

|-
||11:57
||Take '''R'''’s help for all the commands shown in this tutorial.

|-
||12:03
||Import a '''data set''' from the Internet directly or through a file.

|-
||12:08
||This video summarises the Spoken Tutorial project.

|-
||12:13
||If you do not have good bandwidth, you may download and watch it.

|-
||12:17
||We conduct workshops using Spoken Tutorials; give Certificates.

|-
||12:22
||Please contact us.

|-
||12:24
||The Spoken Tutorial project is funded by  MHRD, Govt. of India

|-
||12:30
||Thanks for joining, goodbye.