- class pymc.backends.base.MultiTrace(straces)[source]#
Main interface for accessing values from MCMC results.
The core method to select values is get_values. The method to select sampler statistics is get_sampler_stats. Both kinds of values can also be accessed by indexing the MultiTrace object. Indexing can behave in four ways:
Indexing with a variable or variable name (str) returns all values for that variable, combining values for all chains.
Slicing after the variable name can be used to burn and thin the samples.
>>> trace[varname, 1000:]
For convenience during interactive use, values can also be accessed using the variable as an attribute.
Indexing with an integer returns a dictionary with values for each variable at the given index (corresponding to a single sampling iteration).
Slicing with a range returns a new trace with the number of draws corresponding to the range.
Indexing with the name of a sampler statistic that is not also the name of a variable returns those values from all chains. If there is more than one sampler that provides that statistic, the values are concatenated along a new axis.
For any methods that require a single trace (e.g., taking the length of the MultiTrace instance, which returns the number of draws), the trace with the highest chain number is always used.
- nchains: int
Number of chains in the MultiTrace.
- chains: `List[int]`
List of chain indices
- report: str
Report on the sampling process.
- varnames: `List[str]`
List of variable names in the trace(s)
Get sampler statistics from the trace.
MultiTrace.get_values(varname[, burn, thin, ...])
Get values from traces.
Return a dictionary of point values at idx.
Return an iterator over all or some of the sample points