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---
title: BaseCoherenceFitter
description: API reference for qiskit.ignis.characterization.BaseCoherenceFitter
in_page_toc_min_heading_level: 1
python_api_type: class
python_api_name: qiskit.ignis.characterization.BaseCoherenceFitter
---
# BaseCoherenceFitter
<Class id="qiskit.ignis.characterization.BaseCoherenceFitter" isDedicatedPage={true} github="https://github.com/qiskit-community/qiskit-ignis/tree/stable/0.6/qiskit/ignis/characterization/fitters.py" signature="BaseCoherenceFitter(description, backend_result, xdata, qubits, fit_fun, fit_p0, fit_bounds, circuit_names, series=None, expected_state='0', time_index=0, time_unit='micro-seconds')" modifiers="class">
Bases: `qiskit.ignis.characterization.fitters.BaseFitter`
Base class for fitters of characteristic times
**Parameters**
* **description** (`str`) description of the fitters purpose, e.g. T1.
* **backend\_result** (`Union`\[`Result`, `List`\[`Result`]]) result of execution on the backend.
* **xdata** (`Union`\[`List`\[`float`], `array`]) delay times of the circuits.
* **qubits** (`List`\[`int`]) the qubits to be characterized.
* **fit\_fun** (`Callable`\[…, `float`]) equivalent to parameter f of scipy.curve\_fit.
* **fit\_p0** (`List`\[`float`]) equivalent to parameter p0 of scipy.curve\_fit.
* **fit\_bounds** (`Tuple`\[`List`\[`float`], `List`\[`float`]]) equivalent to parameter bounds of scipy.curve\_fit.
* **circuit\_names** (`List`\[`str`]) names of the circuits, should be the same length as xdata. Full circuit name will be these plus the series name.
* **series** (`Optional`\[`List`\[`str`]]) list of circuit name tags
* **expected\_state** (`str`) is the circuit supposed to end up in 0 or 1?
* **time\_index** (`int`) among parameters of fit\_fun, which one is the characteristic time.
* **time\_unit** (`str`) unit of delay times in xdata.
## Methods
### add\_data
<Function id="qiskit.ignis.characterization.BaseCoherenceFitter.add_data" signature="BaseCoherenceFitter.add_data(results, recalc=True, refit=True)">
Add new execution results to previous execution results
**Parameters**
* **results** (`Union`\[`Result`, `List`\[`Result`]]) new execution results
* **recalc** (`bool`) whether tp recalculate the data
* **refit** (`bool`) whether to refit the data
</Function>
### fit\_data
<Function id="qiskit.ignis.characterization.BaseCoherenceFitter.fit_data" signature="BaseCoherenceFitter.fit_data(qid=- 1, p0=None, bounds=None, series=None)">
Fit the curve.
Compute self.\_params and self.\_params\_err
**Parameters**
* **qid** (`int`) qubit for fitting. If -1 fit for all the qubits
* **p0** (`Optional`\[`List`\[`float`]]) initial guess, equivalent to p0 in scipy.optimize
* **bounds** (`Optional`\[`Tuple`\[`List`\[`float`], `List`\[`float`]]]) bounds, equivalent to bounds in scipy.optimize
* **series** (`Optional`\[`str`]) series to fit (if None fit all)
</Function>
### plot
<Function id="qiskit.ignis.characterization.BaseCoherenceFitter.plot" signature="BaseCoherenceFitter.plot(qind, series, ax=None, show_plot=True)">
Plot coherence data.
**Parameters**
* **qind** (`int`) qubit index to plot
* **series** (`str`) which series to plot (if list then plot multiple)
* **ax** (`Optional`\[`Any`]) plot axes
* **show\_plot** (`bool`) whether to call plt.show()
**Returns**
The axes object
**Return type**
Axes
**Raises**
**ImportError** if matplotlib is not installed
</Function>
### time
<Function id="qiskit.ignis.characterization.BaseCoherenceFitter.time" signature="BaseCoherenceFitter.time(qid=- 1, series='0')">
Return the characteristic time for the given qubit and series
**Parameters**
* **qid** (`int`) the qubit index (or all qubits if -1)
* **series** (`str`) the series to get
**Return type**
`Union`\[`float`, `List`\[`float`]]
**Returns**
The characteristic time of the qubit, or all qubits
</Function>
### time\_err
<Function id="qiskit.ignis.characterization.BaseCoherenceFitter.time_err" signature="BaseCoherenceFitter.time_err(qid=- 1, series='0')">
Return the error of characteristic time for the given qubit and series
**Parameters**
* **qid** (`int`) the qubit index (or all qubits if -1)
* **series** (`str`) the series to get
**Return type**
`Union`\[`float`, `List`\[`float`]]
**Returns**
The error of the characteristic time of the qubit, or all qubits
</Function>
## Attributes
### backend\_result
<Attribute id="qiskit.ignis.characterization.BaseCoherenceFitter.backend_result">
Return the execution results
**Return type**
`Union`\[`Result`, `List`\[`Result`]]
</Attribute>
### description
<Attribute id="qiskit.ignis.characterization.BaseCoherenceFitter.description">
Return the fitters purpose, e.g. T1
**Return type**
`str`
</Attribute>
### fit\_fun
<Attribute id="qiskit.ignis.characterization.BaseCoherenceFitter.fit_fun">
Return the function used in the fit, e.g. BaseFitter.\_exp\_fit\_fun
**Return type**
`Callable`
</Attribute>
### measured\_qubits
<Attribute id="qiskit.ignis.characterization.BaseCoherenceFitter.measured_qubits">
Return the indices of the qubits to be characterized
**Return type**
`List`\[`int`]
</Attribute>
### params
<Attribute id="qiskit.ignis.characterization.BaseCoherenceFitter.params">
Return the fit function parameters that were calculated by curve\_fit
**Return type**
`List`\[`float`]
</Attribute>
### params\_err
<Attribute id="qiskit.ignis.characterization.BaseCoherenceFitter.params_err">
Return the error of the fit function parameters
**Return type**
`List`\[`float`]
</Attribute>
### series
<Attribute id="qiskit.ignis.characterization.BaseCoherenceFitter.series">
Return the list of series for the data
**Return type**
`Optional`\[`List`\[`str`]]
</Attribute>
### xdata
<Attribute id="qiskit.ignis.characterization.BaseCoherenceFitter.xdata">
Return the data points on the x-axis, the independenet parameter which is fit against
**Return type**
`Union`\[`List`\[`float`], `array`]
</Attribute>
### ydata
<Attribute id="qiskit.ignis.characterization.BaseCoherenceFitter.ydata">
Return the data points on the y-axis
The data points are returning in the form of a list of dictionaries:
> * **ydata\[i]\[mean] is a list, where item**
>
> no. j is the probability of success of qubit i for a circuit that lasts xdata\[j].
>
> * **ydata\[i]\[std] is a list, where ydata\[std]\[j] is the**
>
> standard deviation of the success of qubit i.
**Return type**
`List`\[`Dict`]
</Attribute>
</Class>