fast_carpenter.define.systematics module¶
-
class
fast_carpenter.define.systematics.
SystematicWeights
(name, out_dir, weights, out_format='weight_{}', extra_variations=[])[source]¶ Bases:
object
Combines multiple weights and variations to produce a single event weight
To study the impact of systematic uncertainties it is common to re-weight events using a variation of the weights representing, for example, a 1-sigma increase or decrease in the weights. Once there are multiple weight schemes involved writing out each possible combination of these weights becomes tedious and potentially error-prone; this stage makes it easier.
It forms the
nominal
weight for each event by multiplying all nominal weights together, then the specific variation by replacing a given nominal weight with its corresponding “up” or “down” variation.Each variation of a weight should just be a string giving an expression to use for that variation. This stage then combines these into a single expression by joining each set of variations with “*”, i.e. multiplying them together. The final results then use an internal
Define
stage to do the calculation.Parameters: - weights (dictionary[str, dictionary]) – A Dictionary of weight variations
to combine. The keys in this dictionary will determine how this
variation is called in the output variable. The values of this
dictionary should either be a single string – the name of the input
variable to use for the “nominal” variation, or a dictionary containing
any of the keys,
nominal
,up
, ordown
. Each of these should then have a value providing the expression to use for that variation/ - out_format (str) – The format string to use to build the name of the output variations. Defaults to “weight_{}”. Should contain a pair of empty braces which will be replaced with the name for the current variation, e.g. “nominal” or “PileUp_up”.
- extra_variations (list[str]) – A list of additional variations to allow
Other Parameters: - name (str) – The name of this stage (handled automatically by fast-flow)
- out_dir (str) – Where to put the summary table (handled automatically by fast-flow)
Example
syst_weights: energy_scale: {nominal: WeightEnergyScale, up: WeightEnergyScaleUp, down: WeightEnergyScaleDown} trigger: TriggerEfficiency recon: {nominal: ReconEfficiency, up: ReconEfficiency_up}
which will create 4 new variables:
weight_nominal = WeightEnergyScale * TriggerEfficiency * ReconEfficiency weight_energy_scale_up = WeightEnergyScaleUp * TriggerEfficiency * ReconEfficiency weight_energy_scale_down = WeightEnergyScaleDown * TriggerEfficiency * ReconEfficiency weight_recon_up = WeightEnergyScale * TriggerEfficiency * ReconEfficiency_up
- weights (dictionary[str, dictionary]) – A Dictionary of weight variations
to combine. The keys in this dictionary will determine how this
variation is called in the output variable. The values of this
dictionary should either be a single string – the name of the input
variable to use for the “nominal” variation, or a dictionary containing
any of the keys,