fst package

***출처: https://github.com/fstpackage/fst***

매우 빠른 읽기 쓰기 패키지

• 매우 빠른 읽기 쓰기 패키지가 R로 제공
• 심지어 처음부터 데이터의 일부만 읽어오기도 지원
• 전체를 읽어와서 일부만 추출하는게 아니라 처음부터 일부만 불러옴
• 멀티쓰레드를 지원해서 속도도 쓰레드 갯수로 증가 가느

---

# install.packages("devtools")
devtools::install_github("fstPackage/fst", ref = "develop")

## Skipping install of 'fst' from a github remote, the SHA1 (b96aa4b1) has not changed since last install.
##   Use `force = TRUE` to force installation

library(fst)

---

Basic usage

# Generate some random data frame with 10 million rows and various column types
nr_of_rows <- 1e7

df <- data.frame(
    Logical = sample(c(TRUE, FALSE, NA), prob = c(0.85, 0.1, 0.05), nr_of_rows, replace = TRUE),
    Integer = sample(1L:100L, nr_of_rows, replace = TRUE),
    Real = sample(sample(1:10000, 20) / 100, nr_of_rows, replace = TRUE),
    Factor = as.factor(sample(labels(UScitiesD), nr_of_rows, replace = TRUE))
  )

# Store the data frame to disk
  write.fst(df, "dataset.fst")
  
# Retrieve the data frame again
  df <- read.fst("dataset.fst")

## Loading required namespace: data.table

---

Random access

#The fst file format provides full random access to stored datasets. You can retrieve a selection of columns and rows with:
  df_subset <- read.fst("dataset.fst", c("Logical", "Factor"), from = 2000, to = 5000)