Modify nanoarrow arrays — nanoarrow_array

Create a new array or from an existing array, modify one or more parameters. When importing an array from elsewhere, nanoarrow_array_set_schema() is useful to attach the data type information to the array (without this information there is little that nanoarrow can do with the array since its content cannot be otherwise interpreted). nanoarrow_array_modify() can create a shallow copy and modify various parameters to create a new array, including setting children and buffers recursively. These functions power the $<- operator, which can modify one parameter at a time.

Usage

nanoarrow_array_init(schema)

nanoarrow_array_set_schema(array, schema, validate = TRUE)

nanoarrow_array_modify(array, new_values, validate = TRUE)

Arguments

schema: A nanoarrow_schema to attach to this array.
array: A nanoarrow_array.
validate: Use FALSE to skip validation. Skipping validation may result in creating an array that will crash R.
new_values: A named list() of values to replace.

Value

nanoarrow_array_init() returns a possibly invalid but initialized array with a given schema.
nanoarrow_array_set_schema() returns array, invisibly. Note that array is modified in place by reference.
nanoarrow_array_modify() returns a shallow copy of array with the modified parameters such that the original array remains valid.

Examples

nanoarrow_array_init(na_string())
#> <nanoarrow_array string[0]>
#>  $ length    : int 0
#>  $ null_count: int 0
#>  $ offset    : int 0
#>  $ buffers   :List of 3
#>   ..$ :<nanoarrow_buffer validity<bool>[null] ``
#>   ..$ :<nanoarrow_buffer data_offset<int32>[null] ``
#>   ..$ :<nanoarrow_buffer data<string>[null] ``
#>  $ dictionary: NULL
#>  $ children  : list()

# Modify an array using $ and <-
array <- as_nanoarrow_array(1:5)
array$length <- 4
as.vector(array)
#> [1] 1 2 3 4

# Modify potentially more than one component at a time
array <- as_nanoarrow_array(1:5)
as.vector(nanoarrow_array_modify(array, list(length = 4)))
#> [1] 1 2 3 4

# Attach a schema to an array
array <- as_nanoarrow_array(-1L)
nanoarrow_array_set_schema(array, na_uint32())
as.vector(array)
#> [1] 4294967295