Difference between revisions of "R/C2/Plotting-Bar-Charts-and-Scatter-Plot/English"
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Learning Objectives | Learning Objectives | ||
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|| In this tutorial, we will learn how to: | || In this tutorial, we will learn how to: | ||
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* Plot '''scatter plot''' | * Plot '''scatter plot''' | ||
* Find the correlation coefficient between two objects | * Find the correlation coefficient between two objects | ||
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'''moviesSub <- movies[1:20,]''' | '''moviesSub <- movies[1:20,]''' | ||
|| In the '''Source''' window, type the following command. | || In the '''Source''' window, type the following command. | ||
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Save the '''script''' and run the current line by pressing '''Ctrl + Enter '''keys simultaneously. | Save the '''script''' and run the current line by pressing '''Ctrl + Enter '''keys simultaneously. | ||
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* '''ylim''' to set the range of values on Y-axis | * '''ylim''' to set the range of values on Y-axis | ||
* '''main''' for adding a title to the bar chart | * '''main''' for adding a title to the bar chart | ||
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|| Highlight the plot in the '''Plots''' window | || Highlight the plot in the '''Plots''' window | ||
|| However, longer names are being truncated. | || However, longer names are being truncated. | ||
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We can add more arguments to '''barplot''' function for adjusting labels. | We can add more arguments to '''barplot''' function for adjusting labels. | ||
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For more information, please refer to the '''Additional Material''' section on this website. | For more information, please refer to the '''Additional Material''' section on this website. | ||
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|| * '''Scatter plot''' is a graph in which the values of two variables are plotted along two axes. | || * '''Scatter plot''' is a graph in which the values of two variables are plotted along two axes. | ||
* The pattern of the resulting points reveals the correlation. | * The pattern of the resulting points reveals the correlation. | ||
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* Plot '''scatter plot''' | * Plot '''scatter plot''' | ||
* Find the correlation coefficient between two objects | * Find the correlation coefficient between two objects | ||
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* Create a '''scatter plot''' of''' imdb '''underscore '''rating''' and '''imdb '''underscore '''num '''underscore '''votes''' to see their relation. | * Create a '''scatter plot''' of''' imdb '''underscore '''rating''' and '''imdb '''underscore '''num '''underscore '''votes''' to see their relation. | ||
* Save both the plots. | * Save both the plots. | ||
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Spoken Tutorial Workshops | Spoken Tutorial Workshops | ||
|| We conduct workshops using Spoken Tutorials and give certificates. | || We conduct workshops using Spoken Tutorials and give certificates. | ||
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Please contact us. | Please contact us. | ||
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Thank You | Thank You | ||
|| The script for this tutorial was contributed by Tushar Bajaj (TISS Mumbai). | || The script for this tutorial was contributed by Tushar Bajaj (TISS Mumbai). | ||
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This is Sudhakar Kumar from IIT Bombay signing off. Thanks for watching. | This is Sudhakar Kumar from IIT Bombay signing off. Thanks for watching. | ||
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|} | |} | ||
Revision as of 17:32, 27 May 2019
Title of the script: Plotting Bar Charts and Scatter Plots
Author: Tushar Bajaj (TISS Mumbai) and Sudhakar Kumar (IIT Bombay)
Keywords: R, RStudio, graphs, bar chart, labels, scatter plot, correlation, video tutorial, spoken tutorial
| Visual Cue | Narration |
| Show slide
Opening slide |
Welcome to this tutorial on Plotting bar charts and scatter plot. |
| Show slide
Learning Objectives |
In this tutorial, we will learn how to:
|
| Show slide
Pre-requisites |
To understand this tutorial, you should know,
If not, please locate the relevant tutorials R on this website. |
| Show slide
System Specifications |
This tutorial is recorded on* Ubuntu Linux OS version 16.04
Install R version 3.2.0 or higher. |
| Show slide
Download Files |
For this tutorial, we will use
Please download these files from the Code files link of this tutorial. |
| [Computer screen]
Highlight moviesData.csv and barPlots.R in the folder Plots |
I have downloaded and moved these files to Plots folder.
This folder is located in myProject folder on my Desktop. I have also set Plots folder as my Working Directory. |
| Let us switch to Rstudio. | |
| Highlight barPlots.R in the Files window of RStudio | Open the script barPlots.R in RStudio. |
| Highlight the Source button | Run this script by clicking on Source button. |
| Highlight movies in the Source window | movies data frame opens in the Source window. |
| Highlight dim(movies) in the Console window | It has 600 observations of 31 variables. |
| Highlight the scroll bar in the Source window | In the Source window, scroll from left to right. This will enable us to see the remaining objects of movies data frame. |
| Highlight imdb_rating in the Source window | Now, we will learn how to draw a bar chart of the object named imdb underscore rating in movies. |
| Show slide
Bar Chart |
* A bar chart represents data in rectangular bars with length of the bar proportional to the value of the variable.
|
| Let us switch to RStudio. | |
| Highlight movies in the Source window | For the sake of simplicity, we are considering only the first 20 observations of movies to draw a bar chart. |
| Highlight barPlots.R in the Source window | Click on the script barPlots.R |
|
[Rstudio] moviesSub <- movies[1:20,] |
In the Source window, type the following command.
Save the script and run the current line by pressing Ctrl + Enter keys simultaneously. |
| Let me resize the Source window. | |
| Highlight moviesSub in the Environment window | moviesSub with 20 observations is loaded in the Environment.
Now, we draw a bar chart of imdb_rating for these movies. |
| [RStudio]
barplot(moviesSub$imdb_rating, ylab="IMDB Rating", xlab = "Movies", col="blue", ylim=c(0,10), main="Movies' IMDB Rating") |
In the Source window, type the following command. |
| Highlight barplot in the Source window | Here, we have used the following arguments:
|
| Highlight Run button in the Source window | Run the current line. |
| Highlight the plot in the Plots window | The bar chart is displayed with Movies on X-axis and their imdb_rating on Y-axis. |
| Highlight Files and Plots window | In the Plots window, click on Zoom to maximize the plot. |
| Highlight the first bar in the plot | This particular movie has an IMDB rating of approximately 6. |
| Highlight the third bar in the plot | Similarly, this particular movie has an IMDB rating of approximately 8.
However, we do not know the name of the movies. |
| So, we will add more arguments in barplot function to show the names of movies on X-axis. | |
| Close this plot. | |
| [RStudio]
barplot(moviesSub$imdb_rating, ylab="IMDB Rating", col="blue", ylim=c(0,10), main="Movies' IMDB Rating", names.arg=moviesSub$title) |
In the Source window, type the following command. |
| Highlight names.arg in the Source window | Here, we have used the argument names.arg and set it to title.
Remember, title column in moviesSub contains the names of movies. |
| Highlight Run button in the Source window | Run the current line. |
| Highlight Files and Plots window | In the Plots window, click on Zoom to maximize the plot. |
| Highlight X-axis of the plot | Now, the names of movies are displayed on the X-axis.
But not for all movies. This is due to the point that the names are too long to be accommodated. That’s why, we will make these names perpendicular to X-axis. |
| Close this plot. | |
| [RStudio]
barplot(moviesSub$imdb_rating, ylab="IMDB Rating", col="blue", ylim=c(0,10), main="Movies' IMDB Rating", names.arg=moviesSub$title, las = 2) |
In the Source window, type the following command. |
|
Highlight las in the Source window |
Here, we have used las argument.
las equal to 2 produces labels which are at right angles to the axis. |
| Highlight Run button in the Source window | Run the current line. |
| Highlight Files and Plots window | In the Plots window, click on Zoom to maximize the plot. |
| Highlight the plot in the Plots window | Now the names for all the movies are displayed on X-axis.
For example, Filly Brown has an IMDB rating of approximately 6. |
| Highlight the plot in the Plots window | However, longer names are being truncated.
We can add more arguments to barplot function for adjusting labels. For more information, please refer to the Additional Material section on this website. |
| Close this plot. | |
| Highlight movies in the Source window | In the Source window, click on movies. |
| Highlight imdb_rating and audience_score in the Source window | Let us analyze the relation between imdb underscore rating and audience underscore score.
For this, we will draw a scatter plot with these two objects by using plot function. Remember, we have already learnt how to plot a single object. |
| Show Slide
Scatter Plot |
* Scatter plot is a graph in which the values of two variables are plotted along two axes.
|
| Let us switch to RStudio. | |
| Highlight barPlots.R in the Source window | In the Source window, click on the script barPlots.R |
| [RStudio]
plot(x = movies$imdb_rating, y = movies$audience_score, main = "IMDB Rating vs Audience Score", xlab = "IMDB Rating", ylab = "Audience Score", xlim = c(0,10), ylim = c(0,100), col = "blue") |
In the Source window, type the following command. |
| Highlight plot function in the Source window | Here, we have kept imdb underscore rating on the X-axis and audience underscore score on the Y-axis. |
| Highlight xlim in the Source window | As imdb underscore rating of any movie varies between 0 and 10, we have set the range of values on X-axis from 0 to 10. |
| Highlight ylim in the Source window | Similarly, we have set the range of values on Y-axis from 0 to 100. |
| Highlight Run button in the Source window | Save the script and run the current line. |
| Highlight Files and Plots window | In the Plots window, click on Zoom to maximize the plot. |
| Highlight the plot in the Plots window | We can observe that the movies having higher imdb underscore rating has a high audience underscore score. |
| Close this plot. | |
| Now we will learn how to calculate the correlation coefficient between imdb underscore rating and audience underscore score.
For this, we use cor function. | |
| [RStudio]
cor(movies$imdb_rating, movies$audience_score) |
In the Source window, type the following command. |
| Highlight Run button in the Source window | Save the script and run the current line. |
| Highlight the output in the Console window | The correlation coefficient between imdb underscore rating and audience underscore score is evaluated as 0.865. |
| Highlight the output in the Console window | The value of correlation coefficient is always between -1 and +1.
A positive value indicates that the variables are positively related. |
| Let us summarize what we have learnt. | |
| Show slide
Summary |
In this tutorial, we have learnt how to:
|
| Show slide
Assignment |
We now suggest an assignment.
|
| Show slide
About the Spoken Tutorial Project |
The video at the following link summarises the Spoken Tutorial project.
Please download and watch it. |
| Show slide
Spoken Tutorial Workshops |
We conduct workshops using Spoken Tutorials and give certificates.
Please contact us. |
| Show Slide
Forum to answer questions |
Please post your timed queries in this forum. |
| Show Slide
Forum to answer questions |
Please post your general queries in this forum. |
| Show Slide
Textbook Companion |
The FOSSEE team coordinates the TBC project.
For more details, please visit these sites. |
| Show Slide
Acknowledgment |
The Spoken Tutorial project is funded by NMEICT, MHRD, Govt. of India |
| Show Slide
Thank You |
The script for this tutorial was contributed by Tushar Bajaj (TISS Mumbai).
This is Sudhakar Kumar from IIT Bombay signing off. Thanks for watching. |
