rSFSW2: Simulation Framework for SOILWAT2

Description Usage Arguments Value Details Examples

View source: R/OutputDatabase_DataAccess.R

Add new field(s) to a table in dbOutput that is/are based on a calculation of values from (an) existing field(s)

dbOutput_add_calculated_field(
  dbOut_fname,
  table,
  vars_orig,
  vars_new,
  FUN,
  ...,
  overwrite = FALSE,
  verbose = FALSE,
  chunk_size = 1e+05
)

`dbOut_fname`	A character string. The path to the output database.
`table`	A character string. The table name to which the new field(s) should be appended.
`vars_orig`	A vector of character strings. The existing field names that are used by `FUN` to calculate `vars_new`.
`vars_new`	A vector of character strings. The names of new fields. The number must match the number of columns returned by `FUN`.
`FUN`	A function. See details.
`...`	Additional named arguments to `FUN`. See details.
`overwrite`	A logical value. If `vars_new` already exists and `overwrite` is `TRUE`, then the content of the fields `vars_new` will be replaced. If `vars_new` already exists and `overwrite` is `FALSE`, then the function stops with an error.
`verbose`	A logical value.
`chunk_size`	An integer value.

The function is called for its side-effects on dbOut_fname.

The first argument of FUN must be a two-dimensional object. This object contains the extracted values from dbOut_fname, i.e., it has up to chunk_size rows and the columns are vars_orig. Additional arguments can be passed via .... The function must return a value (or values) corresponding to vars_new for each row. These values are inserted into the new field(s).

if (requireNamespace("RSQLite")) {
# Prepare database
dbOut_tmp <- tempfile(fileext = ".sqlite")
con <- RSQLite::dbConnect(RSQLite::SQLite(), dbOut_tmp)
data(iris)
x <- data.frame(P_id = seq_len(nrow(iris)), iris)
RSQLite::dbWriteTable(con, "iris", x)
RSQLite::dbDisconnect(con)

# Define calculation function
vars_orig <- c("Sepal.Length", "Sepal.Width")
example_calc <- function(x, delta = 1, ...) {
  apply(x, MARGIN = 1, function(x) delta * prod(x))
}

# Create new field based on a calculation
dbOutput_add_calculated_field(
  dbOut_fname = dbOut_tmp,
  table = "iris",
  vars_orig = vars_orig,
  vars_new = "calc",
  FUN = example_calc, delta = 2)

# Check the new field
con <- RSQLite::dbConnect(RSQLite::SQLite(), dbOut_tmp)
xout <- RSQLite::dbReadTable(con, "iris")
RSQLite::dbDisconnect(con)

res2 <- example_calc(x[, vars_orig], delta = 2)
all.equal(xout[, "calc"], res2)

# Cleanup
unlink(dbOut_tmp)
}