fst (version 0.9.8)

fst: Access a fst file like a regular data frame

Description

Create a fst_table object that can be accessed like a regular data frame. This object is just a reference to the actual data and requires only a small amount of memory. When data is accessed, only a subset is read from file, depending on the minimum and maximum requested row number. This is possible because the fst file format allows full random access (in columns and rows) to the stored dataset.

Usage

fst(path, old_format = FALSE)

Arguments

path

path to fst file

old_format

must be FALSE, the old fst file format is deprecated and can only be read and converted with fst package versions 0.8.0 to 0.8.10.

Value

An object of class fst_table

Examples

# NOT RUN {
# generate a sample fst file
path <- paste0(tempfile(), ".fst")
write_fst(iris, path)

# create a fst_table object that can be used as a data frame
ft <- fst(path)

# print head and tail
print(ft)

# select columns and rows
x <- ft[10:14, c("Petal.Width", "Species")]

# use the common list interface
ft[TRUE]
ft[c(TRUE, FALSE)]
ft[["Sepal.Length"]]
ft$Petal.Length

# use data frame generics
nrow(ft)
ncol(ft)
dim(ft)
dimnames(ft)
colnames(ft)
rownames(ft)
names(ft)
# }