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---
title: RBFitter
description: API reference for qiskit.ignis.verification.RBFitter
in_page_toc_min_heading_level: 1
python_api_type: class
python_api_name: qiskit.ignis.verification.RBFitter
---
# RBFitter
<Class id="qiskit.ignis.verification.RBFitter" isDedicatedPage={true} github="https://github.com/qiskit-community/qiskit-ignis/tree/stable/0.7/qiskit/ignis/verification/randomized_benchmarking/fitters.py" signature="RBFitter(backend_result, cliff_lengths, rb_pattern=None)" modifiers="class">
Bases: `qiskit.ignis.verification.randomized_benchmarking.fitters.RBFitterBase`
Class for fitters for randomized benchmarking.
**Parameters**
* **backend\_result** ([*Result*](qiskit.result.Result "qiskit.result.Result")) list of results (qiskit.Result).
* **cliff\_lengths** (*list*) the Clifford lengths, 2D list i x j where i is the number of patterns, j is the number of cliffords lengths.
* **rb\_pattern** (*list*) the pattern for the RB sequences.
## Methods
### add\_data
<Function id="qiskit.ignis.verification.RBFitter.add_data" signature="RBFitter.add_data(new_backend_result, rerun_fit=True)">
Add a new result. Re calculate the raw data, means and fit.
**Parameters**
* **new\_backend\_result** (*list*) list of RB results.
* **rerun\_fit** (*bool*) re calculate the means and fit the result.
#### Additional information:
Assumes that the executed result is the output of circuits generated by randomized\_benchmarking\_seq.
</Function>
### calc\_data
<Function id="qiskit.ignis.verification.RBFitter.calc_data" signature="RBFitter.calc_data()">
Retrieve probabilities of success from execution results.
Outputs results into an internal variable \_raw\_data which is a 3-dimensional list, where item (i,j,k) is the probability to measure the ground state for the set of qubits in pattern “i” for seed no. j and vector length self.\_cliff\_lengths\[i]\[k].
#### Additional information:
Assumes that the executed result is the output of circuits generated by randomized\_benchmarking\_seq.
</Function>
### calc\_statistics
<Function id="qiskit.ignis.verification.RBFitter.calc_statistics" signature="RBFitter.calc_statistics()">
Extract averages and std dev from the raw data (self.\_raw\_data).
Assumes that self.\_calc\_data has been run. Output into internal \_ydata variable. ydata is a list of dictionaries (length number of patterns). Dictionary ydata\[i]:
> * ydata\[i]\[mean] is a numpy\_array of length n; entry j of this array contains the mean probability of success over seeds, for vector length self.\_cliff\_lengths\[i]\[j].
> * ydata\[i]\[std] is a numpy\_array of length n; entry j of this array contains the std of the probability of success over seeds, for vector length self.\_cliff\_lengths\[i]\[j].
</Function>
### fit\_data
<Function id="qiskit.ignis.verification.RBFitter.fit_data" signature="RBFitter.fit_data()">
Fit the RB results to an exponential curve.
Fit each of the patterns. Use the data to construct guess values for the fits.
Puts the results into a list of fit dictionaries where each dictionary corresponds to a pattern and has fields:
> * `params` - three parameters of rb\_fit\_fun. The middle one is the exponent.
> * `err` - the error limits of the parameters.
> * `epc` - error per Clifford.
</Function>
### fit\_data\_pattern
<Function id="qiskit.ignis.verification.RBFitter.fit_data_pattern" signature="RBFitter.fit_data_pattern(patt_ind, fit_guess)">
Fit the RB results of a particular pattern to an exponential curve.
**Parameters**
* **patt\_ind** (*int*) index of the data pattern to fit.
* **fit\_guess** (*list*) guess values for the fit.
Puts the results into a list of fit dictionaries where each dictionary corresponds to a pattern and has fields:
> * `params` - three parameters of rb\_fit\_fun. The middle one is the exponent.
> * `err` - the error limits of the parameters.
> * `epc` - error per Clifford.
</Function>
### plot\_rb\_data
<Function id="qiskit.ignis.verification.RBFitter.plot_rb_data" signature="RBFitter.plot_rb_data(pattern_index=0, ax=None, add_label=True, show_plt=True)">
Plot randomized benchmarking data of a single pattern.
**Parameters**
* **pattern\_index** (*int*) which RB pattern to plot.
* **ax** (*Axes*) plot axis (if passed in).
* **add\_label** (*bool*) Add an EPC label.
* **show\_plt** (*bool*) display the plot.
**Raises**
**ImportError** if matplotlib is not installed.
</Function>
## Attributes
### cliff\_lengths
<Attribute id="qiskit.ignis.verification.RBFitter.cliff_lengths">
Return clifford lengths.
</Attribute>
### fit
<Attribute id="qiskit.ignis.verification.RBFitter.fit">
Return fit.
</Attribute>
### raw\_data
<Attribute id="qiskit.ignis.verification.RBFitter.raw_data">
Return raw data.
</Attribute>
### rb\_fit\_fun
<Attribute id="qiskit.ignis.verification.RBFitter.rb_fit_fun">
Return the fit function rb\_fit\_fun.
</Attribute>
### results
<Attribute id="qiskit.ignis.verification.RBFitter.results">
Return all the results.
</Attribute>
### seeds
<Attribute id="qiskit.ignis.verification.RBFitter.seeds">
Return the number of loaded seeds.
</Attribute>
### ydata
<Attribute id="qiskit.ignis.verification.RBFitter.ydata">
Return ydata (means and std devs).
</Attribute>
</Class>