Seleksi elemen data frame (2)

Alih-alih menggunakan angka untuk memilih elemen dari sebuah data frame, Anda juga dapat menggunakan nama variabel untuk memilih kolom dari data frame.

Misalkan Anda ingin memilih tiga elemen pertama dari kolom type. Salah satu caranya adalah

planets_df[1:3,2]

Salah satu kekurangan pendekatan ini adalah Anda harus mengetahui (atau mencari) nomor kolom dari type, yang bisa menyulitkan jika Anda memiliki banyak variabel. Sering kali lebih mudah untuk menggunakan nama variabel secara langsung:

planets_df[1:3,"type"]

Latihan ini merupakan bagian dari kursus

Pengantar R

Instruksi latihan

Pilih dan cetak 5 nilai pertama pada kolom "diameter" dari planets_df.

Latihan interaktif langsung praktik

Cobalah latihan ini dengan melengkapi kode contoh ini.

# The planets_df data frame from the previous exercise is pre-loaded

# Select first 5 values of diameter column

Edit dan Jalankan Kode

Latihan ini merupakan bagian dari kursus

Pengantar R

SkillTag.level.beginnerSkillTag.label

4.8+

Mulai Kursus Gratis

Take your first steps with R. In this chapter, you will learn how to use the console as a calculator and how to assign variables. You will also get to know the basic data types in R. Let's get started.

Exercise 1: How it works Exercise 2: Arithmetic with R Exercise 3: Variable assignment Exercise 4: Variable assignment (2)Exercise 5: Variable assignment (3)Exercise 6: Apples and oranges Exercise 7: Basic data types in R Exercise 8: What's that data type?

We take you on a trip to Vegas, where you will learn how to analyze your gambling results using vectors in R. After completing this chapter, you will be able to create vectors in R, name them, select elements from them, and compare different vectors.

Exercise 1: Create a vector Exercise 2: Create a vector (2)Exercise 3: Create a vector (3)Exercise 4: Naming a vector Exercise 5: Naming a vector (2)Exercise 6: Calculating total winnings Exercise 7: Calculating total winnings (2)Exercise 8: Calculating total winnings (3)Exercise 9: Comparing total winnings Exercise 10: Vector selection: the good times Exercise 11: Vector selection: the good times (2)Exercise 12: Vector selection: the good times (3)Exercise 13: Vector selection: the good times (4)Exercise 14: Selection by comparison - Step 1 Exercise 15: Selection by comparison - Step 2 Exercise 16: Advanced selection

In this chapter, you will learn how to work with matrices in R. By the end of the chapter, you will be able to create matrices and understand how to do basic computations with them. You will analyze the box office numbers of the Star Wars movies and learn how to use matrices in R. May the force be with you!

Exercise 1: What's a matrix?Exercise 2: Analyze matrices, you shall Exercise 3: Naming a matrix Exercise 4: Calculating the worldwide box office Exercise 5: Adding a column for the Worldwide box office Exercise 6: Adding a row Exercise 7: The total box office revenue for the entire saga Exercise 8: Selection of matrix elements Exercise 9: A little arithmetic with matrices Exercise 10: A little arithmetic with matrices (2)

Data often falls into a limited number of categories. For example, human hair color can be categorized as black, brown, blond, red, grey, or white—and perhaps a few more options for people who color their hair. In R, categorical data is stored in factors. Factors are very important in data analysis, so start learning how to create, subset, and compare them now.

Exercise 1: What's a factor and why would you use it?Exercise 2: What's a factor and why would you use it? (2)Exercise 3: What's a factor and why would you use it? (3)Exercise 4: Factor levels Exercise 5: Summarizing a factor Exercise 6: Battle of the sexes Exercise 7: Ordered factors Exercise 8: Ordered factors (2)Exercise 9: Comparing ordered factors

Most datasets you will be working with will be stored as data frames. By the end of this chapter, you will be able to create a data frame, select interesting parts of a data frame, and order a data frame according to certain variables.

Exercise 1: Apa itu data frame?Exercise 2: Cepat, lihat kumpulan data Anda Exercise 3: Lihat struktur datanya Exercise 4: Membuat data frame Exercise 5: Membuat data frame (2)Exercise 6: Seleksi elemen data frame Exercise 7: Seleksi elemen data frame (2)

Latihan Saat Ini

Exercise 8: Hanya planet dengan cincin Exercise 9: Hanya planet dengan cincin (2)Exercise 10: Hanya planet dengan cincin tetapi lebih pendek Exercise 11: Pengurutan Exercise 12: Mengurutkan data frame Anda

As opposed to vectors, lists can hold components of different types, just as your to-do lists can contain different categories of tasks. This chapter will teach you how to create, name, and subset these lists.

Exercise 1: Lists, why would you need them?Exercise 2: Lists, why would you need them? (2)Exercise 3: Creating a list Exercise 4: Creating a named list Exercise 5: Creating a named list (2)Exercise 6: Selecting elements from a list Exercise 7: Creating a new list for another movie