Will calculate the file size, checksum, and checksum authentication method
algorithm automatically if the argument objectName is a file that exists.
Usage
set_physical(
objectName,
id = character(),
numHeaderLines = character(),
numFooterLines = character(),
recordDelimiter = detect_delim(objectName),
fieldDelimiter = ",",
collapseDelimiters = logical(),
literalCharacter = character(),
quoteCharacter = character(),
attributeOrientation = "column",
size = NULL,
sizeUnit = "bytes",
authentication = NULL,
authMethod = NULL,
characterEncoding = character(),
encodingMethod = character(),
compressionMethod = character(),
url = character()
)Arguments
- objectName
name for the object, usually a filename like "hf205-1.csv"
- id
optional, an id value for the <physical> element in EML, for use in referencing
- numHeaderLines
Number of header lines preceding data. Lines are determined by the physicalLineDelimiter, or if it is absent, by the recordDelimiter. This value indicated the number of header lines that should be skipped before starting to parse the data.
Number of footer lines following data. Lines are determined by the physicalLineDelimiter, or if it is absent, by the recordDelimiter. This value indicated the number of footer lines that should be skipped after parsing the data. If this value is omitted, parsers should assume the data continues to the end of the data stream.
- recordDelimiter
This element specifies the record delimiter character when the format is text. The record delimiter is usually a linefeed (\n) on UNIX, a carriage return (\r) on MacOS, or both (\r\n) on Windows/DOS. Multiline records are usually delimited with two line ending characters, for example on UNIX it would be two linefeed characters (\n\n). As record delimiters are often non-printing characters, one can use either the special value "\n" to represent a linefeed (ASCII 0x0a) and "\r" to represent a carriage return (ASCII 0x0d). Alternatively, one can use the hex value to represent character values (e.g., 0x0a).
- fieldDelimiter
"," character by default (for csv files). This element specifies a character to be used in the object for indicating the ending column for an attribute. The delimiter character itself is not part of the attribute value, but rather is present in the column following the last character of the value. Typical delimiter characters include commas, tabs, spaces, and semicolons. The only time the fieldDelimiter character is not interpreted as a delimiter is if it is contained in a quoted string (see quoteCharacter) or is immediately preceded by a literalCharacter. Non-printable quote characters can be provided as their hex values, and for tab characters by its ASCII string "\t". Processors should assume that the field starts in the column following the previous field if the previous field was fixed, or in the column following the delimiter from the previous field if the previous field was delimited.
- collapseDelimiters
The collapseDelimiters element specifies whether sequential delimiters should be treated as a single delimiter or multiple delimiters. An example is when a space delimiter is used; often there may be several repeated spaces that should be treated as a single delimiter, but not always. The valid values are yes or no. If it is set to yes, then consecutive delimiters will be collapsed to one. If set to no or absent, then consecutive delimiters will be treated as separate delimiters. Default behavior is no; hence, consecutive delimiters will be treated as separate delimiters, by default.
- literalCharacter
This element specifies a character to be used for escaping special character values so that they are treated as literal values. This allows "escaping" for special characters like quotes, commas, and spaces when they are intended to be used in an attribute value rather than being intended as a delimiter. The literalCharacter is typically a \.
- quoteCharacter
This element specifies a character to be used in the object for quoting values so that field delimiters can be used within the value. This basically allows delimiter "escaping". The quoteChacter is typically a " or '. When a processor encounters a quote character, it should not interpret any following characters as a delimiter until a matching quote character has been encountered (i.e., quotes come in pairs). It is an error to not provide a closing quote before the record ends. Non-printable quote characters can be provided as their hex values.
- attributeOrientation
Specifies whether the attributes described in the physical stream are found in columns or rows. The valid values are column or row. If set to 'column', then the attributes are in columns. If set to 'row', then the attributes are in rows. Row orientation is rare.
- size
This element contains information of the physical size of the entity, by default represented in bytes unless the sizeUnit attribute is provided to change the units.
- sizeUnit
the unit in which size is measured; default is 'bytes'
- authentication
This element describes authentication procedures or techniques, typically by giving a checksum value for the object. The method used to compute the authentication value (e.g., MD5) is listed in the method attribute.
- authMethod
the method for authentication checksum, e.g. MD5
- characterEncoding
This element contains the name of the character encoding. This is typically ASCII or UTF-8, or one of the other common encodings.
- encodingMethod
This element lists a encoding method used to encode the object, such as base64, BinHex.
- compressionMethod
This element lists a compression method used to compress the object, such as zip, compress, etc. Compression and encoding methods must be listed in the order in which they were applied, so that decompression and decoding should occur in the reverse order of the listing. For example, if a file is compressed using zip and then encoded using MIME base64, the compression method would be listed first and the encoding method second.
- url
optional. The complete url from which the data file can be downloaded, if possible.
Value
an EML physical object, such as used in a dataTable element to define the format of the data file.
Examples
set_physical("hf205-01-TPexp1.csv")
#> $objectName
#> [1] "hf205-01-TPexp1.csv"
#>
#> $size
#> NULL
#>
#> $authentication
#> $authentication$authentication
#> NULL
#>
#> $authentication$method
#> NULL
#>
#>
#> $compressionMethod
#> character(0)
#>
#> $encodingMethod
#> character(0)
#>
#> $characterEncoding
#> character(0)
#>
#> $dataFormat
#> $dataFormat$textFormat
#> $dataFormat$textFormat$numHeaderLines
#> character(0)
#>
#> $dataFormat$textFormat$numFooterLines
#> character(0)
#>
#> $dataFormat$textFormat$recordDelimiter
#> [1] "\r\n"
#>
#> $dataFormat$textFormat$attributeOrientation
#> [1] "column"
#>
#> $dataFormat$textFormat$simpleDelimited
#> $dataFormat$textFormat$simpleDelimited$fieldDelimiter
#> [1] ","
#>
#> $dataFormat$textFormat$simpleDelimited$collapseDelimiters
#> character(0)
#>
#> $dataFormat$textFormat$simpleDelimited$quoteCharacter
#> character(0)
#>
#> $dataFormat$textFormat$simpleDelimited$literalCharacter
#> character(0)
#>
#>
#>
#>
#> $id
#> character(0)
#>
#> $distribution
#> list()
#>
# FIXME set recordDelimiter based on user's system?
# FIXME richer distribution options? use set_distribution at top level?