Part 16 — Reshape & Merge

Fundamental Series — Part 16 of 20

Dua operasi penting: reshape (mengubah bentuk wide ↔︎ long) dan merge (menggabungkan tabel).

Wide → Long — `pivot_longer()`

library(tidyr)
library(dplyr)

df_wide <- tibble(
  nama = c("Andi", "Budi"),
  math = c(80, 90),
  sains = c(75, 85),
  bahasa = c(88, 92)
)

df_long <- df_wide |>
  pivot_longer(
    cols = math:bahasa,
    names_to = "mata_pelajaran",
    values_to = "nilai"
  )

Long → Wide — `pivot_wider()`

df_long |>
  pivot_wider(
    names_from = mata_pelajaran,
    values_from = nilai
  )

Join / Merge

siswa <- tibble(
  id = 1:4,
  nama = c("Andi", "Budi", "Citra", "Dina")
)

nilai <- tibble(
  id = c(1, 2, 3, 5),
  skor = c(80, 90, 75, 85)
)

Jenis Join

# Left join — semua dari kiri, match dari kanan
siswa |> left_join(nilai, join_by(id))

# Inner join — hanya yang match
siswa |> inner_join(nilai, join_by(id))

# Full join — semua dari kedua tabel
siswa |> full_join(nilai, join_by(id))

# Anti join — di kiri tapi TIDAK di kanan
siswa |> anti_join(nilai, join_by(id))

`bind_rows()` dan `bind_cols()`

df1 <- tibble(nama = c("A", "B"), x = 1:2)
df2 <- tibble(nama = c("C", "D"), x = 3:4)

# Tumpuk vertikal
bind_rows(df1, df2)

# Gabung horizontal (harus jumlah baris sama)
bind_cols(df1, df2)

Latihan

Latihan 16.1 — Reshape

# Data GDP per tahun (wide)
gdp <- tibble(
  negara = c("Indonesia", "Malaysia", "Thailand"),
  `2020` = c(1060, 337, 500),
  `2021` = c(1186, 373, 506),
  `2022` = c(1319, 407, 536)
)

# 1. Pivot ke long (kolom: negara, tahun, gdp)
# 2. Pivot kembali ke wide

Latihan 16.2 — Join

produk <- tibble(id = 1:3, nama = c("A", "B", "C"))
penjualan <- tibble(id = c(1, 1, 2, 4), jumlah = c(10, 20, 15, 5))

# 1. Left join — semua produk + penjualan
# 2. Anti join — produk yang tidak punya penjualan
# 3. Inner join — hanya yang match

Ringkasan

Fungsi	Keterangan
`pivot_longer()`	Wide → Long
`pivot_wider()`	Long → Wide
`left_join()`	Join: semua kiri
`inner_join()`	Join: hanya match
`full_join()`	Join: semua
`anti_join()`	Baris yang tidak match
`bind_rows()`	Tumpuk vertikal

Sebelumnya: Part 15 — Group & Summarise Selanjutnya: Part 17 — Apply & Vectorisasi

--- title: "Part 16 — Reshape & Merge" description: "Mengubah bentuk data dan menggabungkan tabel di R: pivot_longer, pivot_wider, left_join, dan bind_rows." date: "2026-02-26" categories: [Fundamental, Reshape] series: "Fundamental Programming" order: 16 --- ## Fundamental Series — Part 16 of 20 Dua operasi penting: **reshape** (mengubah bentuk wide ↔ long) dan **merge** (menggabungkan tabel). --- ## Wide → Long — `pivot_longer()` ```r library(tidyr) library(dplyr) df_wide <- tibble( nama = c("Andi", "Budi"), math = c(80, 90), sains = c(75, 85), bahasa = c(88, 92) ) df_long <- df_wide |> pivot_longer( cols = math:bahasa, names_to = "mata_pelajaran", values_to = "nilai" ) ``` --- ## Long → Wide — `pivot_wider()` ```r df_long |> pivot_wider( names_from = mata_pelajaran, values_from = nilai ) ``` --- ## Join / Merge ```r siswa <- tibble( id = 1:4, nama = c("Andi", "Budi", "Citra", "Dina") ) nilai <- tibble( id = c(1, 2, 3, 5), skor = c(80, 90, 75, 85) ) ``` ### Jenis Join ```r # Left join — semua dari kiri, match dari kanan siswa |> left_join(nilai, join_by(id)) # Inner join — hanya yang match siswa |> inner_join(nilai, join_by(id)) # Full join — semua dari kedua tabel siswa |> full_join(nilai, join_by(id)) # Anti join — di kiri tapi TIDAK di kanan siswa |> anti_join(nilai, join_by(id)) ``` --- ## `bind_rows()` dan `bind_cols()` ```r df1 <- tibble(nama = c("A", "B"), x = 1:2) df2 <- tibble(nama = c("C", "D"), x = 3:4) # Tumpuk vertikal bind_rows(df1, df2) # Gabung horizontal (harus jumlah baris sama) bind_cols(df1, df2) ``` --- ## Latihan ::: {.callout-caution} ## Latihan 16.1 — Reshape ```r # Data GDP per tahun (wide) gdp <- tibble( negara = c("Indonesia", "Malaysia", "Thailand"), `2020` = c(1060, 337, 500), `2021` = c(1186, 373, 506), `2022` = c(1319, 407, 536) ) # 1. Pivot ke long (kolom: negara, tahun, gdp) # 2. Pivot kembali ke wide ``` ::: ::: {.callout-caution} ## Latihan 16.2 — Join ```r produk <- tibble(id = 1:3, nama = c("A", "B", "C")) penjualan <- tibble(id = c(1, 1, 2, 4), jumlah = c(10, 20, 15, 5)) # 1. Left join — semua produk + penjualan # 2. Anti join — produk yang tidak punya penjualan # 3. Inner join — hanya yang match ``` ::: --- ## Ringkasan | Fungsi | Keterangan | |--------|-----------| | `pivot_longer()` | Wide → Long | | `pivot_wider()` | Long → Wide | | `left_join()` | Join: semua kiri | | `inner_join()` | Join: hanya match | | `full_join()` | Join: semua | | `anti_join()` | Baris yang tidak match | | `bind_rows()` | Tumpuk vertikal | --- *Sebelumnya: [Part 15 — Group & Summarise](../2026_02_26_15_group_summarise/index.qmd)* *Selanjutnya: [Part 17 — Apply & Vectorisasi](../2026_02_26_17_apply/index.qmd)*

Fundamental Series — Part 16 of 20

Wide → Long — pivot_longer()

Long → Wide — pivot_wider()