assign_slice {rquery}

Assign a value to a slice of data (set of rows meeting a condition, and specified set of columns).

Description

Uses if_else_block.

Usage

assign_slice(source, testexpr, columns, value, env = parent.frame())

Arguments

source

optree relop node or data.frame.

testexpr

character containing the test expression.

columns

character vector of column names to alter.

value

value to set in matching rows and columns (scalar).

env

environment to look to.

Details

Note: ifebtest_* is a reserved column name for this procedure.

Value

optree or data.frame.

Examples

if (requireNamespace("DBI", quietly = TRUE) && requireNamespace("RSQLite", quietly = TRUE)) {
  my_db <- DBI::dbConnect(RSQLite::SQLite(), ":memory:")
  d <- rq_copy_to(
    my_db,
    'd',
    data.frame(i = c(1, 2, 3, 4, 5, 6, 7, 8, 9, 10),
               a = c(0, 0, 1, 1, 1, 1, 1, 1, 1, 1),
               b = c(0, 1, 0, 1, 1, 1, 1, 1, 1, 1),
               r = runif(10)),
    temporary=TRUE, overwrite=TRUE)

  optree <- d %.>%
    assign_slice(.,
                 testexpr = qe(r<0.5),
                 columns = qc(a, b),
                 value = 2)
  cat(format(optree))

  sql <- to_sql(optree, my_db)
  cat(sql)

  print(DBI::dbGetQuery(my_db, sql))

  DBI::dbDisconnect(my_db)
}