velociraptor.observations.objects module

Objects for observational data plotting.

Tools for adding in extra (e.g. observational) data to plots.

Includes an object container and helper functions for creating and reading files.

velociraptor.observations.objects.save_cosmology(handle: h5py._hl.files.File, cosmology: astropy.cosmology.core.Cosmology)

Save the (astropy) cosmology to a HDF5 dataset.

Parameters:

• handle (h5py.File) – h5py file handle to save the cosmology to. This is performed by creating a cosmology group and setting attributes.
• cosmology (astropy.cosmology.Cosmology) – The Astropy cosmology instance to save to the HDF5 file. This is performed by extracting all of the key variables and saving them as either floating point numbers or strings.

Notes

This process can be reversed by using load_cosmology.

velociraptor.observations.objects.load_cosmology(handle: h5py._hl.files.File)

Save the (astropy) cosmology to a HDF5 dataset.

Parameters:handle (h5py.File) – h5py file handle to read the cosmology from. Returns:Astropy cosmology instance extracted from the HDF5 file. Return type:astropy.cosmology.Cosmology

class velociraptor.observations.objects.ObservationalData

Bases: object

Observational data object. Contains routines for both writing and reading HDF5 files containing the observations, as well as plotting.

name

Name of the observation for users to identifty

Type:str

x_units

Units for horizontal axes

Type:unyt_quantity

y_units

Units for vertical axes

Type:unyt_quantity

x

Horizontal data points

Type:unyt_array

y

Vertical data points

Type:unyt_array

x_scatter

Scatter in horizontal direction. Can be None, or an unyt_array of shape 1XN (symmetric) or 2XN (non-symmetric) such that it can be passed to plt.errorbar easily.

Type:Union[unyt_array, None]

y_scatter

Scatter in vertical direction. Can be None, or an unyt_array of shape 1XN (symmetric) or 2XN (non-symmetric) such that it can be passed to plt.errorbar easily.

Type:Union[unyt_array, None]

x_comoving

Whether or not the horizontal values are comoving (True) or physical (False)

Type:bool

y_comoving

Whether or not the vertical values are comoving (True) or physical (False)

Type:bool

x_description

Default label for horizontal axis (without units), also a description of the variable.

Type:str

y_description

Default label for horizontal axis (without units), also a description of the variable.

Type:str

filename

Filename that the data was read from, or was written to.

Type:str

comment

A free-text comment describing the data, including e.g. which cosmology and IMF it is calibrated to.

Type:str

citation

Short citation for data, e.g. Author et al. (Year) (Project), such as Baldry et al. (2012) (GAMA)

Type:str

bibcode

Bibcode for citation, this can be found on the NASA ADS.

Type:str

redshift

Redshift at which the data is collected at. If a range, use the mid-point.

Type:float

redshift_lower

Lowest redshift at which the data is collected at. Used to determine whether it should be plotted on a given figure.

Type:float

redshift_upper

Highest redshift at which the data is collected at. Used to determine whether it should be plotted on a given figure.

Type:float

plot_as

Whether the data should be plotted as points (typical for observations) or as a line (typical for simulation data). Allowed values:

• points
• line

Type:Union[str, None]

cosmology

Astropy cosmology that the data has been corrected to.

Type:Cosmology

plot_as = None

load(filename: str, prefix: Optional[str] = None)

Loads the observations from file.

Parameters:

• filename (str) – The filename to load the data from. Probably should end in .hdf5.
• prefix (str, optional) – An optional prefix to all fields that enables multiple observational datasets to be saved in a single file. Not for general use, only within MultiRedshiftObservationalData. If a prefix is used, cosmology is not saved.

write(filename: str, prefix: Optional[str] = None)

Writes the observations to file.

Parameters:

• filename (str) – The filename to write the data to. Probably should end in .hdf5.
• prefix (str, optional) – An optional prefix to all fields that enables multiple observational datasets to be saved in a single file. Not for general use, only within MultiRedshiftObservationalData. If a prefix is used, cosmology is not saved.

associate_x(array: unyt.array.unyt_array, scatter: Optional[unyt.array.unyt_array], comoving: bool, description: str)

Associate an x quantity with this observational data instance.

Parameters:

• array (unyt_array) – The array of (horizontal) data points, including units.
• scatter (Union[unyt_array, None]) – The array of scatter (1XN or 2XN) in the horizontal co-ordinates with associated units.
• comoving (bool) – Whether or not the horizontal values are comoving.
• description (str) – Short description of the data, e.g. Stellar Masses

associate_y(array: unyt.array.unyt_array, scatter: Optional[unyt.array.unyt_array], comoving: bool, description: str)

Associate an y quantity with this observational data instance.

Parameters:

• array (unyt_array) – The array of (vertical) data points, including units.
• scatter (Union[unyt_array, None]) – The array of scatter (1XN or 2XN) in the vertical co-ordinates with associated units.
• comoving (bool) – Whether or not the vertical values are comoving.
• description (str) – Short description of the data, e.g. Stellar Masses

associate_citation(citation: str, bibcode: str)

Associate a citation with this observational data instance.

Parameters:

• citation (str) – Short citation, formatted as follows: Author et al. (Year) (Project), e.g. Baldry et al. (2012) (GAMA)
• bibcode (str) – Bibcode for the paper the data was extracted from, available from the NASA ADS or publisher. E.g. 2012MNRAS.421..621B

associate_name(name: str)

Associate a name with this observational data instance.

Parameters:name (str) – Short name to describe the dataset.

associate_comment(comment: str)

Associate a comment with this observational data instance.

Parameters:comment (str) – A free-text comment describing the data, including e.g. which cosmology and IMF it is calibrated to.

associate_redshift(redshift: float, redshift_lower: Optional[float] = None, redshift_upper: Optional[float] = None)

Associate the redshift that the observations were taken at with this observational data instance.

Parameters:

• redshift (float) – Redshift at which the data is collected at. If a range, use the mid-point.
• redshift_lower (Optional[float]) – Lower bound for this set of observations. Used to determine if plotting is viable, and should always be present in the case where a multiple redshift dataset is used.
• redshift_upper (Optional[float]) – Upper bound for this set of observations. Used to determine if plotting is viable, and should always be present in the case where a multiple redshift dataset is used.

associate_plot_as(plot_as: str)

Associate the ‘plot_as’ field - this should either be line or points.

Parameters:plot_as (str) – Either points or line

associate_cosmology(cosmology: astropy.cosmology.core.Cosmology)

Associate a cosmology with this dataset that it has been corrected for. This should be an astropy cosmology instance.

Parameters:cosmology (astropy.cosmology.Cosmology) – Astropy cosmology instance describing what cosmology the data has been corrected to.

plot_on_axes(axes: matplotlib.axes._axes.Axes, errorbar_kwargs: Optional[dict] = None)

Plot this set of observational data as an errorbar().

Parameters:

• axes (plt.Axes) – The matplotlib axes to plot the data on. This will either plot the data as a line or a set of errorbar points, with the short citation (self.citation) being included in the legend automatically.
• errorbar_kwargs (dict) – Optional keyword arguments to pass to plt.errorbar.

class velociraptor.observations.objects.MultiRedshiftObservationalData

Bases: object

Multi-redshift version of ObservationalData class, which should be used instead of the ObservationalData class for reading files, and writing multiple redshift files.

Essentially, this contains multiple instances of ObservationalData, and allows for multiple redshift data to be read transparently.

code_version = '0.16.1'

maximum_number_of_returns = 1024

get_datasets_overlapping_with(redshifts: List[float] = [0.0, 1000.0]) → List[velociraptor.observations.objects.ObservationalData]

Gets individual redshift datasets overlapping with the specified redshift range. The check is performed inclusively, so if you ask for overlaps with [0.25, 0.75], and an observation has a redshift range of [0.75, 1.25], it will be included. Note that maximum_number_of_returns modifies the behaviour of this function, and the maximum length of the returned list will be the same as that attribute.

Parameters:redshifts (List[float]) – Redshifts to check for overlaps with. This defaults to the range [0.0, 1000.0], and hence should overlap with all reasonable datasets.

Notes

You can access this ability in a slightly more user-friendly way using the velociraptor.observations.load_observations() function.

Datasets are returned in order of their scale-factor proximity to the centre of the range specified in redshifts.

associate_dataset(dataset: velociraptor.observations.objects.ObservationalData)

Associate an individual redshift dataset with this object.

Parameters:dataset (ObservationalData) – Instance of ObservationalData that may or may not be completed; comments are handled at the top level and are over-written. In total, citation, bibcode, name, comment, and cosmology are shared.

associate_citation(citation: str, bibcode: str)

Associate a citation with this observational data instance.

Parameters:

• citation (str) – Short citation, formatted as follows: Author et al. (Year) (Project), e.g. Baldry et al. (2012) (GAMA)
• bibcode (str) – Bibcode for the paper the data was extracted from, available from the NASA ADS or publisher. E.g. 2012MNRAS.421..621B

associate_name(name: str)

Associate a name with this observational data instance.

Parameters:name (str) – Short name to describe the dataset.

associate_comment(comment: str)

Associate a comment with this observational data instance.

Parameters:comment (str) – A free-text comment describing the data, including e.g. which cosmology and IMF it is calibrated to.

associate_cosmology(cosmology: astropy.cosmology.core.Cosmology)

Associate a cosmology with this dataset that it has been corrected for. This should be an astropy cosmology instance.

Parameters:cosmology (astropy.cosmology.Cosmology) – Astropy cosmology instance describing what cosmology the data has been corrected to.

associate_maximum_number_of_returns(maximum_number_of_returns: int)

Associate a maximum number of returned datasets with this object. This number will give the maximum number of datasets that are returned in a call to load_datasets. This is particularly useful in the case where you want to provide a large number of fits and only want to show a single curve on the figure.

Parameters:maximum_number_of_returns (int) – The maximum number of datasets to plot simultaneously.

write(filename: str)

Writes all of the datasets currently present in the object to a HDF5 file.

Parameters:filename (str) – File to be written to, including the .hdf5.

load(filename: str)

Reads all of the datasets from an associated file to the object.

Parameters:filename (str) – File to be read from, including the .hdf5.