MaskedColumn¶

class astropy.table.MaskedColumn(data=None, name=None, mask=None, fill_value=None, dtype=None, shape=(), length=0, description=None, unit=None, format=None, meta=None, copy=False, copy_indices=True)[source]¶

Bases: Column, _MaskedColumnGetitemShim, MaskedArray

Define a masked data column for use in a Table object.

Parameters:

datapython:list, ndarray, or python:None: Column data values
namepython:str: Column name and key for reference within Table
maskpython:list, ndarray or python:None: Boolean mask for which True indicates missing or invalid data
fill_valuepython:float, python:int, python:str, or python:None: Value used when filling masked column elements
dtypedtypeastropy:-like: Data type for column
shapepython:tuple or (): Dimensions of a single row element in the column data
lengthpython:int or 0: Number of row elements in column data
descriptionpython:str or python:None: Full description of column
unitpython:str or python:None: Physical unit
formatpython:str, python:None, or python:callable(): Format string for outputting column values. This can be an “old-style” (format % value) or “new-style” (str.format) format specification string or a function or any callable object that accepts a single value and returns a string.
metadict-like or python:None: Meta-data associated with the column

Examples

A MaskedColumn is similar to a Column except that it includes mask and fill_value attributes. It can be created in two different ways:

Provide a data value but not shape or length (which are inferred from the data).

Examples:
```
col = MaskedColumn(data=[1, 2], name='name')
col = MaskedColumn(data=[1, 2], name='name', mask=[True, False])
col = MaskedColumn(data=[1, 2], name='name', dtype=float, fill_value=99)
```
The mask argument will be cast as a boolean array and specifies which elements are considered to be missing or invalid.

The dtype argument can be any value which is an acceptable fixed-size data-type initializer for the numpy.dtype() method. See https://numpy.org/doc/stable/reference/arrays.dtypes.html. Examples include:
- Python non-string type (float, int, bool)
- Numpy non-string type (e.g. np.float32, np.int64, np.bool_)
- Numpy.dtype array-protocol type strings (e.g. ‘i4’, ‘f8’, ‘S15’)
If no dtype value is provide then the type is inferred using np.array(data). When data is provided then the shape and length arguments are ignored.
Provide length and optionally shape, but not data

Examples:
```
col = MaskedColumn(name='name', length=5)
col = MaskedColumn(name='name', dtype=int, length=10, shape=(3,4))
```
The default dtype is np.float64. The shape argument is the array shape of a single cell in the column.

To access the Column data as a raw numpy.ma.MaskedArray object, you can use one of the data or value attributes (which are equivalent):

col.data
col.value

Attributes Summary

`data`	The plain MaskedArray data held by this column.
`fill_value`	The filling value of the masked array is a scalar.
`info`	Container for meta information like name, description, format.
`name`	The name of this column.

Methods Summary

`convert_unit_to`(new_unit[, equivalencies])	Converts the values of the column in-place from the current unit to the given unit.
`copy`([order, data, copy_data])	Return a copy of the current instance.
`filled`([fill_value])	Return a copy of self, with masked values filled with a given value.
`insert`(obj, values[, mask, axis])	Insert values along the given axis before the given indices and return a new `MaskedColumn` object.
`more`([max_lines, show_name, show_unit])	Interactively browse column with a paging interface.
`pformat`([max_lines, show_name, show_unit, ...])	Return a list of formatted string representation of column values.
`pprint`([max_lines, show_name, show_unit, ...])	Print a formatted string representation of column values.

Attributes Documentation

data¶: The plain MaskedArray data held by this column.

fill_value¶

info¶

Container for meta information like name, description, format.

This is required when the object is used as a mixin column within a table, but can be used as a general way to store meta information. In this case it just adds the mask_val attribute.

name¶: The name of this column.

Methods Documentation

convert_unit_to(new_unit, equivalencies=[])¶

Converts the values of the column in-place from the current unit to the given unit.

To change the unit associated with this column without actually changing the data values, simply set the unit property.

Parameters:

new_unitpython:str or astropy.units.UnitBase instance: The unit to convert to.
equivalenciespython:list of python:tuple: A list of equivalence pairs to try if the unit are not directly convertible. See Equivalencies.

Raises:

astropy.units.UnitsError: If units are inconsistent

copy(order='C', data=None, copy_data=True)¶

Return a copy of the current instance.

If data is supplied then a view (reference) of data is used, and copy_data is ignored.

Parameters:

order{‘C’, ‘F’, ‘A’, ‘K’}, optional: Controls the memory layout of the copy. ‘C’ means C-order, ‘F’ means F-order, ‘A’ means ‘F’ if a is Fortran contiguous, ‘C’ otherwise. ‘K’ means match the layout of a as closely as possible. (Note that this function and :func:numpy.copy are very similar, but have different default values for their order= arguments.) Default is ‘C’.
dataarray, optional: If supplied then use a view of data instead of the instance data. This allows copying the instance attributes and meta.
copy_databool, optional: Make a copy of the internal numpy array instead of using a reference. Default is True.

Returns:

colColumn or MaskedColumn: Copy of the current column (same type as original)

filled(fill_value=None)[source]¶

Return a copy of self, with masked values filled with a given value.

Parameters:

fill_valuescalar; optional: The value to use for invalid entries (None by default). If None, the fill_value attribute of the array is used instead.

Returns:

filled_columnColumn: A copy of self with masked entries replaced by fill_value (be it the function argument or the attribute of self).

insert(obj, values, mask=None, axis=0)[source]¶

Insert values along the given axis before the given indices and return a new MaskedColumn object.

Parameters:

objpython:int, slice or python:sequence of python:int: Object that defines the index or indices before which values is inserted.
valuesnumpy:array_like: Value(s) to insert. If the type of values is different from that of the column, values is converted to the matching type. values should be shaped so that it can be broadcast appropriately.
maskbool or numpy:array_like: Mask value(s) to insert. If not supplied, and values does not have a mask either, then False is used.
axispython:int, optional: Axis along which to insert values. If axis is None then the column array is flattened before insertion. Default is 0, which will insert a row.

Returns:

outMaskedColumn: A copy of column with values and mask inserted. Note that the insertion does not occur in-place: a new masked column is returned.

more(max_lines=None, show_name=True, show_unit=False)¶

Interactively browse column with a paging interface.

Supported keys:

f, <space> : forward one page
b : back one page
r : refresh same page
n : next row
p : previous row
< : go to beginning
> : go to end
q : quit browsing
h : print this help

Parameters:

max_linespython:int: Maximum number of lines in table output.
show_namebool: Include a header row for column names. Default is True.
show_unitbool: Include a header row for unit. Default is False.

pformat(max_lines=None, show_name=True, show_unit=False, show_dtype=False, html=False)¶

Return a list of formatted string representation of column values.

If no value of max_lines is supplied then the height of the screen terminal is used to set max_lines. If the terminal height cannot be determined then the default will be determined using the astropy.conf.max_lines configuration item. If a negative value of max_lines is supplied then there is no line limit applied.

Parameters:

max_linespython:int: Maximum lines of output (header + data rows)
show_namebool: Include column name. Default is True.
show_unitbool: Include a header row for unit. Default is False.
show_dtypebool: Include column dtype. Default is False.
htmlbool: Format the output as an HTML table. Default is False.

Returns:

linespython:list: List of lines with header and formatted column values

pprint(max_lines=None, show_name=True, show_unit=False, show_dtype=False)¶

Print a formatted string representation of column values.

If no value of max_lines is supplied then the height of the screen terminal is used to set max_lines. If the terminal height cannot be determined then the default will be determined using the astropy.conf.max_lines configuration item. If a negative value of max_lines is supplied then there is no line limit applied.

Parameters:

max_linespython:int: Maximum number of values in output
show_namebool: Include column name. Default is True.
show_unitbool: Include a header row for unit. Default is False.
show_dtypebool: Include column dtype. Default is True.

Navigation

MaskedColumn¶