Question

Using R studio

1. Read the iris data set into a data frame.

2. Print the first few lines of the iris dataset.

3. Output all the entries with Sepal Length > 5.

4. Plot a box plot of Petal Length with a color of your choice.

5. Plot a histogram of Sepal Width.

6. Plot a scatter plot showing the relationship between Petal Length and Petal Width.

7. Find the mean of Sepal Length by species. Hint: You could use the tapply function. Other methods are also acceptable.

8. Use the subset function to extract only rows where the species is "versicolor."

9. Install the dplyr package and load it on your console.

10. Use a function in the dplyr package to show only rows with Sepal Length <6 belonging to species "virginica."

Answer 1

Code:

#Library Dataset was used.
#Loading dataset iris
library(datasets)
data(iris)

#1) reading dataset into a data frame.
cat("dataloaded in data frame\n\n")
data <- data.frame(iris)

#2) first few lines of iris dataset.
cat("few lines of dataset\n\n")
head(data)
cat("\n\n")

Output:

#3) Output all the entries with Sepal Length > 5.
cat("entries with Sepal Length > 5\n\n")
ans1 <- data[(data[,1]>5),]
ans1
cat("\n\n")

Output:

Note: The output of this question is large please run it on your PC and save the Output.

#4) Plot a box plot of Petal Length with a color of your choice.
cat("boxplot of petal length\n\n")
boxplot(Petal.Length ~ Species, data=iris,
main="Box Plot",
col="red",
xlab="Species",
ylab="Sepal Length")
cat("\n\n")

Output:

#5) histogram of Sepal Width
cat("Histogram of sepal width\n\n")
sepal_width <- data$Sepal.Width
hist(sepal_width)
cat("\n\n")

Output:

#6) scatter plot showing the relationship between Petal Length and Petal Width.
cat("Scatter plot\n\n")
plot(data$Petal.Length, data$Petal.Width)
cat("\n\n")

Output:

#7) Find the mean of Sepal Length by species.
cat("mean of Sepal Length by species\n\n")
mean <- tapply(iris$Sepal.Length, iris$Species, mean)
mean
cat("\n\n")

Output:

#8) Use the subset function to extract only rows where the species is "versicolor."
cat("subset function to extract only rows\n\n")
irisV <- subset(data, Species == "versicolor")
irisV
cat("\n\n")

Output:

#Note: Please Write this in your R console and install the library.
install.packages("dplyr")

#10) only rows with Sepal Length <6 belonging to species "virginica."
library(dplyr)
cat("Sepal Length <6 belonging to species virginica\n\n")
ans <- filter(data, species == "virginica", sepal.length < 6)
ans

Output:

Explanation to code:

1) Library function is used to load a library in R.
2) Data function is used to load a specific dataset with name as argument.
3) data.frame is used to frame the data which we have take from the iris dataset.
4) Head function is used to print the first few values of the data frame.

Detailed Explanation:
1) ans1 <- data[(data[,1]>5),]

• In this code we are taking the dataframe data we are selecting the first column and checking if it is greater than 5 or not.

2) boxplot(Petal.Length ~ Species, data=iris,
main="Box Plot Q4",
col="red",
xlab="Species",
ylab="Sepal Length")

• In this code we have used boxplot function. It has arguments i.e. against which two of the variable you have to make the plot. Main is the name of the plot. Col is used to colour the box. xlab and ylab are the label to the plot.

3) sepal_width <- data$Sepal.Width
hist(sepal_width)

• We are taking the sepal width in a variable and then plotting a histogram using the function hist.

4) plot(data$Petal.Length, data$Petal.Width)

• In this code we have plotted a scatter plot with the help of the function plot. It take two argument i.e. X and Y variable for the plot.

5) mean <- tapply(iris$Sepal.Length, iris$Species, mean)

• In this code we have used the function tapply and we have given 3 arguments i.e. sepal length, special and mean.

6)  irisV <- subset(data, Species == "versicolor")

• In this code we have used subset and them we have find out the subset of the data where species is versicolor.

7) ans <- filter(data, species == "virginica", sepal.length < 6)

• In this code we have used the function filter which come under dplyr. We have passed arguments like data , species which virginica and the condition that the sepal length should be < 6.

Note: You can refer the R documentation for more information regarding the function these are related just from the assignment.

Screenshot of code: