LaF (version 0.5)

laf_open: Create a connection to a file using a data model.

Description

Uses a data model to create a connection to a file. The data model contains all the information needed to open the file (column types, column widths, etc.).

Usage

laf_open(model, ...)

Arguments

model

A data_model{data model}.

...

Additional arguments can be used to overwrite the values specified by the data model.

Value

• Object of type laf. Values can be extracted from this object using indexing, and methods such as read_lines, next_block.

Details

Depending on the field `type' laf_open uses laf_open_csv and laf_open_fwf to open the file. The data model should contain all information needed by these routines to open the file.

See Also

See read_dm and detect_dm_csv for ways of creating data models.

Examples

# Generate test data
ntest <- 10
column_types <- c("integer", "integer", "double", "string")
testdata <- data.frame(
    a = 1:ntest,
    b = sample(1:2, ntest, replace=TRUE),
    c = round(runif(ntest), 13),
    d = sample(c("jan", "pier", "tjores", "corneel"), ntest, replace=TRUE)
    )
# Write test data to csv file
write.table(testdata, file="tmp.csv", row.names=FALSE, col.names=FALSE, sep=',')

# Create LaF-object
laf <- laf_open_csv("tmp.csv", column_types=column_types)

# Write data model to file
write_dm(laf, "tmp.yaml")

# Read data model and open file
laf <- laf_open(read_dm("tmp.yaml"))

# Write test data to second csv file
write.table(testdata, file="tmp2.csv", row.names=FALSE, col.names=FALSE, sep=',')

# Read data model and open seconde file, demonstrating the use of the optional
# arguments to laf_open
laf2 <- laf_open(read_dm("tmp.yaml"), filename="tmp2.csv")