Indexing and Subsetting - Practical

Preface

Open Rstudio to do the practicals. Note that tasks with * are optional.

R packages

In this practical, a number of R packages are used. The packages used (with versions that were used to generate the solutions) are:

survival (version: 3.5.7)

R version 4.3.2 (2023-10-31 ucrt)

Dataset

For this practical, we will use the heart and retinopathy data sets from the survival package. More details about the data sets can be found in:

https://stat.ethz.ch/R-manual/R-devel/library/survival/html/heart.html

https://stat.ethz.ch/R-manual/R-devel/library/survival/html/retinopathy.html

Indexing and Subsetting

Sometimes we want to obtain a subset of the data sets before investigating the descriptive statistics and performing the statistical analysis.

Indexing

Task 1

Using the heart data set:

Select the first row.
Select the first column.
Select the column surgery.

Task 2

Create a matrix that takes the values 1:4 and has 2 rows and 2 columns. You can name this object mat. Select the second row of all columns.

Task 3

Create an array that consists of 2 matrices. Matrix 1 will consist of the values 1:4 and matrix 2 will consist of the values 5:8. Both matrices will have 2 columns and 2 rows. Give the name ar1 to the this array. Select the 2nd row of all columns from each matrix.

Subsetting

Task 1

Using the retinopathy data set:

Select the futime for all adult patients.
Select all the variables for patients that received treatment.

Task 2

Using the retinopathy data set:

Select the age for patients that have futime more than 20.
Select the age for patients that have futime more than 20 and are adults.
Select patients that have no missing values in age.

Task 3

Using the retinopathy data set:

Select only the rows of the left eye.
Select only the rows of adult patients.