Data Analysis using R
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Questions and Answers

Which command is used to remove all objects from the R workspace?

  • rm(list=ls(all=TRUE)) (correct)
  • remove.objects()
  • rm(list=all)
  • clear()

The function mean() can be used to calculate the median of a set of numbers.

False (B)

What is the syntax to create a vector called 'y' containing the values 1, 5, 4, and 8?

y=c(1,5,4,8)

The function used to load a saved workspace in R is called _____

<p>load</p> Signup and view all the answers

Match the following R commands with their functions:

<p>getwd() = Get the working directory setwd() = Set the working directory ls() = List objects in the workspace save.image() = Save the current workspace</p> Signup and view all the answers

Which function would you use to check for missing values in a dataset?

<p>is.na() (D)</p> Signup and view all the answers

The function na.omit() removes rows that contain any missing values.

<p>True (A)</p> Signup and view all the answers

What is the main purpose of the complete.cases() function?

<p>To select rows with no missing values.</p> Signup and view all the answers

To create a dataframe in R using vectors for age, gender, and weight, you would use the function data.frame() with the vectors named as ___.

<p>a, g, w</p> Signup and view all the answers

Match the following R functions with their purposes:

<p>is.na() = Checks for missing values na.omit() = Removes individuals with missing values subset() = Selects specific rows or columns from a dataframe data.frame() = Creates a dataframe from vectors</p> Signup and view all the answers

What command is used to install the Ecdat package in R?

<p>install.packages('Ecdat') (D)</p> Signup and view all the answers

The command library('datasets') is used to load the datasets package into the R workspace.

<p>True (A)</p> Signup and view all the answers

How can you access the weight of the first individual in the 'data' dataframe created from age, gender, and weight vectors?

<p>data[1,3]</p> Signup and view all the answers

What happens when you execute 'mean(y, na.rm = TRUE)' in R?

<p>It calculates the mean excluding NA values. (B)</p> Signup and view all the answers

A dataframe in R can be created by importing text or Excel files.

<p>True (A)</p> Signup and view all the answers

What function is used to import a text file into R?

<p>read.table</p> Signup and view all the answers

The command to display the first six rows of a dataframe is ____.

<p>head()</p> Signup and view all the answers

Match the following dataframe functions with their purposes:

<p>dim() = Shows the number of observations and variables rownames() = Displays the names of the rows colnames() = Displays the names of the columns tail() = Shows the last six lines</p> Signup and view all the answers

When importing a dataframe from an Excel file, what is the first step you should take in RStudio?

<p>Select the folder where the Excel file is located. (C)</p> Signup and view all the answers

The function 'merge()' is used to sort a dataframe according to a variable.

<p>False (B)</p> Signup and view all the answers

What would be the output of 'class(nobel)' after importing the dataframe?

<p>data.frame</p> Signup and view all the answers

To create a vector in R containing the values 29020, 32500, and 40320, one could use the command ____.

<p>c(29020, 32500, 40320)</p> Signup and view all the answers

Which of the following statements regarding dataframes is false?

<p>You can only create dataframes by importing files. (B)</p> Signup and view all the answers

Flashcards

Dataframe in R

A data structure in R that stores a table of data, with rows representing observations and columns representing variables.

Creating a dataframe

Methods to create a dataframe in R include importing from files (text or excel), direct creation, or using existing data.

Importing from text/Excel

A method to create a dataframe in R by reading data from text files, comma separated value (csv) files, or spreadsheet files. Commonly used for data load.

read.table function

A function in R to import data from text-based files. It’s often used for loading data from comma separated values (.csv) or tab separated values (.tsv) files.

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dataframe dimensions

The number of rows and columns in a dataframe, useful for understanding the dataset size. Determined by the dim() function in R.

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Row/Column Names

The names of the rows (observations) and columns (variables) in a dataframe. Used for accessing data by specific names.

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head() function

Displays the first 6 rows of a dataframe to preview the data.

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tail() function

Displays the last 6 rows of a dataframe to quickly check the end of data.

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subset()

A function in R to retrieve specific parts of a dataframe based on logical conditions on variables.

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merge()

A function used to combine two dataframes, aligning rows based on similar variables.

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order() function

A function used to sort rows in a dataframe based on values in a specific column.

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NA value in R

Represents Missing values in R. Often have to be handled when calculating or working with the data

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Managing Missing Values

Dealing with 'NA' (Not Available) values in datasets, crucial for accurate analysis.

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R Database

A database managed using the R programming language.

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R Workspace

A temporary space in RStudio for storing variables, vectors, matrices, lists, and data frames. These are called objects in R.

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is.na()

A function to identify missing values in a dataset.

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complete.cases()

Selects rows of a dataframe with no missing values.

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ls()

A function used to display a list of all objects in the current R workspace.

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rm(list=ls(all=TRUE))

A command to remove all objects from the R workspace.

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na.omit()

Removes rows with at least one missing value.

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Subset(dataframe)

Extracting specific rows or columns of a dataset using criteria.

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getwd()

A function used to display the current working directory in R.

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setwd()

A function used to change the current working directory in R.

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Dataframe generation

Creating a structured table (dataframe) with rows and columns to store data.

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save.image()

A command to save the entire R workspace to a file.

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Dataframe variables

Individual columns in a dataframe, each representing specific data.

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load()

A function to load an R workspace previously saved with save.image().

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mtcars data

A dataset containing information about 32 car models, useful for analysis.

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Variable (in R)

A named location in R that stores a value.

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chicken data

A dataset about weights and food consumption of chickens.

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quakes data

Earthquake data showing earthquake magnitude locations.

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Vector (in R)

An ordered sequence of values in R (e.g., numbers or characters).

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Ecdat package

Database package in R with pre-loaded datasets.

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Class of object (in R)

The type of a variable or vector, like numeric, character, or data frame in R.

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cbind()

Combines data horizontally (columns).

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DoctorAUS data

A dataset containing information from analysis in the health sector.

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Dataset Search Tool

Online tool for searching existing datasets.

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rbind()

Combines data vertically (rows).

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Function (in R)

A block of code that performs a specific task in R.

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mean()

Calculates the arithmetic mean of values in R.

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NA (in R)

Represents missing data values.

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Study Notes

Data Analysis using R

  • R is a programming language and software environment for statistical computing and graphics
  • RStudio is a desktop environment for R
  • R Data analysis involves creating, uploading and using a database in R
  • Workspace in RStudio includes variables, mathematical vectors, matrices, lists, and dataframes
  • To show objects in a workspace, use ls().
  • To remove all objects in a workspace use rm(list=ls(all=TRUE))
  • To select a folder for saving the workspace use getwd() and setwd("C:/name/name/name")
  • To save the workspace to a file use save.image("name.Rdata")
  • To load the saved workspace use load("name.Rdata")
  • Variables are assigned values using the equal sign (=) for example, x = 1.
  • class(x) shows the object type.
  • A vector is created using y=c(1,5,4,8).
  • The command class(y) displays the object type
  • Matrices can be created from vectors using functions like rbind() and cbind() for example m = rbind(y, z).
  • R functions are used for importing and exporting data, performing operations, generating graphs
  • Functions generally use the form function_name(par1=value1, par2=value2, …)
  • Using ?mean displays the help for the mean function
  • Using the is.na() function indicates missing values, like missing data is denoted NA (Not Applicable) in R
  • mean(y, na.rm = TRUE) removes NAs when calculating mean.
  • A dataframe is a table with observations in rows and variables in columns
  • Dataframes can be created in R by importing from a text or excel file
  • The read.table function allows importing text files. header = TRUE shows that the first row contains column names

Dataframe Basic Functions

  • dim() shows the number of observations and variables.
  • rownames() shows names of rows.
  • colnames() shows names of columns.
  • head() displays the first six rows of a dataframe.
  • tail() displays the last six rows of a dataframe

Dataframe Advanced Functions

  • subset() is used to select sections of a dataframe
  • subset(dataframe, subset = logical_expression, select = list_of_variables)
  • merge(df1, df2, by = list_of_variables, by.x = ,by.y = ,….) joins two dataframes.
  • df[order(df$nom_var),] sorts the dataframe based on a column named "nom_var".

Exercise: Age and Creativity of Researchers

  • Calculate the age in which scientists are highly creative using year_research_mid and year_birth data
  • Calculate the average age using the mean() function
  • Dataframes to include Nobel prize winners' characteristics, including the year when research was conducted and year of birth

Exercise 2: Age and Creativity of Researchers

  • Calculate the average age at which scientists did their research before 1905.
  • Calculate the average age at which scientists did their research after 1985.

Exercise 3: Lifespan Calculation

  • Calculate the lifespan of each research using the difference between their birth year and death year (nobel$year_death - nobel$year_birth).
  • Calculate the average lifespan using the mean() function on the new lifespan column.

Managing Missing Values

  • Problem in calculating the average lifespan with missing value.
  • is.na() identifies missing values.
  • complete.cases() selects rows without missing values.
  • na.omit() removes rows with any missing values.

2) Dataframe Generation

  • Create a dataframe from sample data including age, gender, and weight of 5 individuals

3) Dataframes in R or Database Packages

  • Various data packages already existing in R

Example 1: Motor Trend US Magazine

  • Data on 32 car models (1973–74)
  • A table of their data

Example 2: Weight and Food of Chickens in a Chicken Coop

  • Data on the weight and feed of chickens

Example 3: Earthquake Magnitude in Fiji

  • Data displaying distribution of earthquake magnitudes near Fiji from 1964
  • Online tool for searching data sets

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Description

This quiz explores the fundamentals of data analysis using R programming and RStudio. Participants will review concepts such as workspace management, data handling, and object manipulation. Test your knowledge on how to effectively create and manage datasets in R.

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