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Aggregate function: returns the first value in a group.

Usage

first(x, ...)

# S4 method for SparkDataFrame
first(x)

# S4 method for characterOrColumn
first(x, na.rm = FALSE)

Arguments

x

a SparkDataFrame or a column used in aggregation function.

...

further arguments to be passed to or from other methods.

na.rm

a logical value indicating whether NA values should be stripped before the computation proceeds.

Details

The function by default returns the first values it sees. It will return the first non-missing value it sees when na.rm is set to true. If all values are missing, then NA is returned. Note: the function is non-deterministic because its results depends on the order of the rows which may be non-deterministic after a shuffle.

Note

first(SparkDataFrame) since 1.4.0

first(characterOrColumn) since 1.4.0

Examples

if (FALSE) {
sparkR.session()
path <- "path/to/file.json"
df <- read.json(path)
first(df)
}
if (FALSE) {
first(df$c)
first(df$c, TRUE)
}