# Drift Fault Demo

This tutorial will walk you through:

- creating a fault instance
- creating an injector instance
- using the injector to inject a fault into data
- visualize the results

## Setup and import packages

Import DriftFault and other packages that are used in this tutorial

```python
import sys
import os

# Add the repo root to sys.path
repo_root = os.path.abspath(os.path.join("..", "src"))
if repo_root not in sys.path:
    sys.path.insert(0, repo_root)


from fault_injector.injector import Injector
from fault_injector.visualizer import FaultVisualizer
from fault_injector.fault_lib import *
import numpy as np
import matplotlib.pyplot as plt
```

## Starting Data

Generate random generated data using the `DataGen` library. This data will serve as the sensor data for this experiment.

Any list or array of numeric values can replace the `original_value` variable in this tutorial.

```python
    def plot_values(values, size):
        """
        this function can be used to plot the randomly generated data. To generate this data, see `random_gen` method.
        """
        max_val = max(values)
        min_val = min(values)

        # calculate the middle of the extremes
        y_mid =  (max_val - min_val) / 2 + min_val

        # set the y_max to 2 times the mid. This center the data points on the y axis
        y_max = y_mid * 2

        fig, ax = plt.subplots()
        # plot the generated data
        ax.plot(values, color="blue")

        # plot a horizontal line across the middle
        ax.hlines(y=y_mid, xmin=0, xmax=size, color="red")

        ax.set(xlabel="time", ylabel="value")

        # ylim assumes the values are positive
        ax.set_ylim([0, y_max])
        ax.grid()

        plt.show()
```

```python
rand_max = 0.52
rand_min = 0.48
size = 500

# generate synthetic data
original_values = np.random.uniform(rand_min, rand_max, size)
plot_values(original_values, size)
```

Generated Data

![original](../../images/demos/drift_fault/original.png)

## Define Fault

This example will utilize the `DriftFault` library to create an instance of the drift fault. The `DriftFault` expects the `params` variable to be equal to a dictionary containing the key `drift_rate`. `drift_rate` corresponds to the slope of the fault delta. The larger the `drift_rate` value is, the faster the fault will drift away from the true value. A `drift_rate` of zero corresponds to no change from the true value.

```python
fault_params = {"drift_rate": 0.0001}
fault_obj = DriftFault(params=fault_params)
```

## Define Injector

The `Injector` library will be used for the injector instance. This instance take in `fault` and `params`.

`fault` expects a fault object, just like the one created in the previous step.

`params` expects a dictionary with two keys: `start` and `stop`. These keys correspond to the starting and ending indices for the list/array of numeric values that will receive the fault. In this example, the indices that receive the fault range from 100 to 400.

```python
injector_params = {"start":100,
                   "stop": 400}
injector_object = Injector(fault=fault_obj,
                           params=injector_params)
```

## Inject Fault

Use the `inject_fault` method of the `Injector` object to inject the fault. This method expects the `x` variable to be set equal to a list or array of numeric values. This represents the true values prior to receiving a fault. For this example, the `original_values` variable that was generated earlier will be used.

```python
new_values = injector_object.inject_fault(x=original_values)
```

## Compare Original to New Values

To visualize the fault, we will examine the Fault delta, then plot the new values compared to the true values.

```python
# initiate the visualizer
vis = FaultVisualizer()

vis.plot_fault_delta(original_values, new_values, title='Fault Delta')
```

Fault Delta

![delta](../../images/demos/drift_fault/delta.png)

```python
vis.plot_comparison(original_values, new_values, title='Comparison')
```

Fault Comparison

![comparison](../../images/demos/drift_fault/comparison.png)