RxTextData

Cikk
07/12/2022

revoscalepy.RxTextData(file: str, strings_as_factors: bool = False,
    column_classes: dict = None, column_info: dict = None,
    vars_to_keep: list = None, vars_to_drop: list = None,
    missing_value_string: str = 'NA', rows_per_read: int = 500000,
    delimiter: str = None, combine_delimiters: bool = False,
    quote_mark: str = '"', decimal_point: str = '.',
    thousands_separator: str = None,
    read_date_format: str = '[%y[-][/]%m[-][/]%d]',
    read_posixct_format: str = '%y[-][/]%m[-][/]%d [%H:%M[:%S]][%p]',
    century_cutoff: int = 20, first_row_is_column_names=None,
    rows_to_sniff: int = 10000, rows_to_skip: int = 0,
    return_data_frame: bool = True,
    default_read_buffer_size: int = 10000,
    default_decimal_column_type: str = None,
    default_missing_column_type: str = None,
    write_precision: int = 7, strip_zeros: bool = False,
    quoted_delimiters: bool = False, is_fixed_format: bool = None,
    use_fast_read: bool = True, create_file_set: bool = None,
    rows_per_out_file: int = None, verbose: int = 0,
    check_vars_to_keep: bool = False, file_system: typing.Union[str,
    revoscalepy.datasource.RxFileSystem.RxFileSystem] = 'native',
    input_encoding: str = 'utf-8',
    write_factors_as_indexes: bool = False)

Description

Main generator for class RxTextData, which extends RxDataSource.

Arguments

file

Character string specifying a text file. If it has an ‘.sts’ extension, it is interpreted as a fixed format schema file. If the column_info argument contains start and width information, it is interpreted as a fixed format data file. Otherwise, it is treated as a delimited text data file. See the Details section for more information on using ‘.sts’ files.

return_data_frame

Bool value indicating whether or not to convert the result from a list to a data frame (for use in rxReadNext only). If False, a list is returned.

strings_as_factors

Bool value indicating whether or not to automatically convert strings to factors on import. This can be overridden by specifying “character” in column_classes and column_info. If True, the factor levels will be coded in the order encountered. Since this factor level ordering is row dependent, the preferred method for handling factor columns is to use column_info with specified “levels”.

column_classes

Dictionary of column names to strings specifying the column types to use when converting the data. The element names for the vector are used to identify which column should be converted to which type.

Allowable column types are:

”bool” (stored as uchar),
“integer” (stored as int32),
“float32” (the default for floating point data for ‘.xdf’ files),
“numeric” (stored as float64 as in R),
“character” (stored as string),
“factor” (stored as uint32),
“ordered” (ordered factor stored as uint32. Ordered factors are treated
    the same as factors in RevoScaleR analysis functions.),

”int16” (alternative to integer for smaller storage space),
“uint16” (alternative to unsigned integer for smaller storage space),
“Date” (stored as Date, i.e. float64. Not supported if use_fast_read =
    True.)

”POSIXct” (stored as POSIXct, i.e. float64. Not supported if
    use_fast_read = True.)

Note for “factor” and “ordered” types, the levels will be coded in the order encountered. Since this factor level ordering is row dependent, the preferred method for handling factor columns is to use column_info with specified “levels”.

column_info

List of named variable information lists. Each variable information list contains one or more of the named elements given below. When importing fixed format data, either column_info or an ‘.sts’ schema file should be supplied. For such fixed format data, only the variables specified will be imported. For all text types, the information supplied for column_info overrides that supplied for column_classes.

Currently available properties for a column information list are:

type: Character string specifying the data type for the column. See
    column_classes argument description for the available types. If the
    type is not specified for fixed format data, it will be read as
    character data.

newName: Character string specifying a new name for the variable.
description: Character string specifying a description for the variable.
levels: List of strings containing the levels when type = “factor”. If
    the levels property is not provided, factor levels will be determined
    by the values in the source column. If levels are provided, any value
    that does not match a provided level will be converted to a missing
    value.

newLevels: New or replacement levels specified for a column of type
    “factor”. It must be used in conjunction with the levels argument.
    After reading in the original data, the labels for each level will be
    replaced with the newLevels.

low: The minimum data value in the variable (used in computations using
    the F() function.

high: The maximum data value in the variable (used in computations
    using the F() function.

start: The left-most position, in bytes, for the column of a fixed
    format file respectively. When all elements of column_info have
    “start”, the text file is designated as a fixed format file. When none
    of the elements have it, the text file is designated as a delimited
    file. Specification of start must always be accompanied by
    specification of width.

width: The number of characters in a fixed-width character column or
    the column of a fixed format file. If width is specified for a
    character column, it will be imported as a fixed-width character
    variable. Any characters beyond the fixed width will be ignored.
    Specification of width is required for all columns of a fixed format
    file (if not provided in an ‘.sts’ file).

decimalPlaces: The number of decimal places.
index: Column index in the original delimited text data file. It is
    used as an alternative to naming the variable information list if the
    original delimited text file does not contain column names. Ignored if
    a name for the list is specified. Should not be used with fixed format
    files.

vars_to_keep

List of strings of variable names to include when reading from the input data file. If None, argument is ignored. Cannot be used with vars_to_drop.

vars_to_drop

List of strings of variable names to exclude when reading from the input data file. If None, argument is ignored. Cannot be used with vars_to_keep.

missing_value_string

Character string containing the missing value code. It can be an empty string: “”.

rows_per_read

Number of rows to read at a time.

delimiter

Character string containing the character to use as the separator between variables. If None and the column_info argument does not contain “start” and “width” information (which implies a fixed-formatted file), the delimiter is auto-sensed from the list “,”, ” “, “;”, and ” “.

combine_delimiters

Bool value indicating whether or not to treat consecutive non-space (” “) delimiters as a single delimiter. Space ” ” delimiters are always combined.

quote_mark

Character string containing the quotation mark. It can be an empty string: “”.

decimal_point

Character string containing the decimal point. Not supported when use_fast_read is set to True.

thousands_separator

Character string containing the thousands separator. Not supported when use_fast_read is set to True.

read_date_format

Character string containing the time date format to use during read operations. Not supported when use_fast_read is set to True. Valid formats are:

%c Skip a single character (see also %w).
%Nc Skip N characters.
%$c Skip the rest of the input string.
%d Day of the month as integer (01-31).
%m Month as integer (01-12) or as character string.
%w Skip a whitespace delimited word (see also %c).
%y Year. If less than 100, century_cutoff is used to determine the actual
year.
%Y Year as found in the input string.
%%, %[, %] input the %, [, and ] characters from the input string.
[…] square brackets within format specifications indicate optional
components; if present, they are used, but they need not be there.

read_posixct_format

Character string containing the time date format to use during read operations. Not supported when use_fast_read is set to True. Valid formats are:

%c Skip a single character (see also %w).
%Nc Skip N characters.
%$c Skip the rest of the input string.
%d Day of the month as integer (01-31).
%H Hour as integer (00-23).
%m Month as integer (01-12) or as character string.
%M Minute as integer (00-59).
%n Milliseconds as integer (00-999).
%N Milliseconds or tenths or hundredths of second.
%p Character string defining ‘am’/‘pm’.
%S Second as integer (00-59).
%w Skip a whitespace delimited word (see also %c).
%y Year. If less than 100, century_cutoff is used to determine the actual
year.
%Y Year as found in the input string.
%%, %[, %] input the %, [, and ] characters from the input string.
[…] square brackets within format specifications indicate optional
components; if present, they are used, but they need not be there.

century_cutoff

Integer specifying the changeover year between the twentieth and twenty-first century if two-digit years are read. Values less than century_cutoff are prefixed by 20 and those greater than or equal to century_cutoff are prefixed by 19. If you specify 0, all two digit dates are interpreted as years in the twentieth century. Not supported when use_fast_read is set to True.

first_row_is_column_names

Bool indicating if the first row represents column names for reading text. If first_row_is_column_names is None, then column names are auto- detected. The logic for auto-detection is: if the first row contains all values that are interpreted as character and the second row contains at least one value that is interpreted as numeric, then the first row is considered to be column names; otherwise the first row is considered to be the first data row. Not relevant for fixed format data. As for writing, it specifies to write column names as the first row. If first_row_is_column_names is None, the default is to write the column names as the first row.

rows_to_sniff

Number of rows to use in determining column type.

rows_to_skip

Integer indicating number of leading rows to ignore. Only supported for use_fast_read = True.

default_read_buffer_size

Number of rows to read into a temporary buffer. This value could affect the speed of import.

default_decimal_column_type

Used to specify a column’s data type when only decimal values (possibly mixed with missing (NA) values) are encountered upon first read of the data and the column’s type information is not specified via column_info or column_classes. Supported types are “float32” and “numeric”, for 32-bit floating point and 64-bit floating point values, respectively.

default_missing_column_type

Used to specify a given column’s data type when only missings (NAs) or blanks are encountered upon first read of the data and the column’s type information is not specified via column_info or column_classes. Supported types are “float32”, “numeric”, and “character” for 32-bit floating point, 64-bit floating point and string values, respectively. Only supported for use_fast_read = True.

write_precision

Integer specifying the precision to use when writing numeric data to a file.

strip_zeros

Bool value if True, if there are only zeros after the decimal point for a numeric, it will be written as an integer to a file.

quoted_delimiters

Bool value, if True, delimiters within quoted strings will be ignored. This requires a slower parsing process. Only applicable to use_fast_read is set to True; delimiters within quotes are always supported when use_fast_read is set to False.

is_fixed_format

Bool value, if true, the input data file is treated as a fixed format file. Fixed format files must have a ‘.sts’ file or a column_info argument specifying the start and width of each variable. If False, the input data file is treated as a delimited text file. If None, the text file type (fixed or delimited text) is auto-determined.

use_fast_read

None or bool value. If True, the data file is accessed directly by the Microsoft R Services Compute Engine. If False, StatTransfer is used to access the data file. If None, the type of text import is auto-determined. use_fast_read should be set to False if importing Date or POSIXct data types, if the data set contains the delimiter character inside a quoted string, if the decimalPoint is not “.”, if the thousandsSeparator is not “,”, if the quoteMark is not “”“, or if combineDelimiters is set to True. use_fast_read should be set to True if rowsToSkip or defaultMissingColType are set. If use_fast_read is True, by default variables containing the values True and False or T and F will be created as bool variables. use_fast_read cannot be set to False if an HDFS file system is being used. If an incompatible setting of use_fast_read is detected, a warning will be issued and the value will be changed.

create_file_set

Bool value or None. Used only when writing. If True, a file folder of text files will be created instead of a single text file. A directory will be created whose name is the same as the text file that would otherwise be created, but with no extension. In the directory, the data will be split across a set of text files (see rows_per_out_file below for determining how many rows of data will be in each file). If False, a single text file will be created. If None, a folder of files will be created if the input data set is a composite XDF file or a folder of text files. This argument is ignored if the text file is fixed format.

rows_per_out_file

Integer value or None. If a directory of text files is being created, this will be the number of rows of data put into each file in the directory.

verbose

Integer value. If 0, no additional output is printed. If 1, information on the text type (text or textFast) is printed.

check_vars_to_keep

bool value. If True variable names specified in vars_to_keep will be checked against variables in the data set to make sure they exist. An error will be reported if not found. If there are more than 500 variables in the data set, this flag is ignored and no checking is performed.

file_system

Character string or RxFileSystem object indicating type of file system; “native” or RxNativeFileSystem object can be used for the local operating system.

input_encoding

Character string indicating the encoding used by input text. May be set to either “utf-8” (the default), or “gb18030”, a standard Chinese encoding. Not supported when use_fast_read is set to True.

write_factors_as_indexes

bool. If True, when writing to an RxTextData data source, underlying factor indexes will be written instead of the string representations. Not supported when use_fast_read is set to False.

Returns

Object of class RxTextData.

Example

import os
from revoscalepy import RxOptions, RxTextData, rx_get_info
sample_data_path = RxOptions.get_option("sampleDataDir")
text_data_source = RxTextData(os.path.join(sample_data_path, "AirlineDemoSmall.csv"))
results = rx_get_info(data = text_data_source)
print(results)

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