Solved: plot confidence interval matplotlib

Matplotlib is a powerful plotting library used in Python programing language. It provides an object-oriented API for embedding plots into applications that use general-purpose GUI toolkits like Tkinter, wxPython, or Qt. One of the important tools provided by Matplotlib is the capability of creating a confidence interval plot.

Confidence interval, as a statistical term, refers to the degree of certainty in a sampling method. A confidence level tells you how sure you can be, expressed as a percentage. For instance, a 99% confidence level suggests that each of your probability estimates is likely to be accurate 99% of the time.

Creating a Confidence Interval Plot Using Matplotlib

Creating a confidence interval plot in Matplotlib involves several steps. Let’s delve into the explanation of the corresponding Python code to accomplish these steps:

First, we have to import the necessary libraries:

```import matplotlib.pyplot as plt
import numpy as np
from scipy.stats import sem, t
from scipy import mean
```

Now, we can calculate the confidence interval following these steps.

1. Determine a random dataset for which we will calculate the confidence interval.
2. Calculate the mean and standard error of the dataset.
3. Determine the margin of error for the confidence interval.
4. Finally, calculate the range of the confidence interval.

Here’s the Python code corresponding to these steps.

```confidence = 0.95
data = np.random.rand(100)
n = len(data)
m = mean(data)
std_err = sem(data)
h = std_err * t.ppf((1 + confidence) / 2, n - 1)

start = m - h
end = m + h
```

The variable ‘confidence’ is the confidence level expressed as a percentage, and ‘data’ contains the random dataset. The mean and standard error are computed by the ‘mean’ and ‘sem’ function of SciPy library respectively. The margin of error ‘h’ is determined by multiplying the standard error by the t-score, which we fetch from the t-distribution using the ‘ppf’ function. Lastly, we calculate the range of the confidence interval.

Plotting the Confidence Interval in Matplotlib

In this final section of the code, we are utilizing Matplotlib to visualize the confidence interval.

```plt.figure(figsize=(9,6))
plt.bar(np.arange(len(data)), data)
plt.fill_between(np.arange(len(data)), start, end, color='b', alpha=0.1)
plt.title('Confidence Interval')
plt.show()
```

It uses a bar plot to display the data and ‘fill_between’ method to represent the confidence interval. The ‘figure’ function initializes a new figure and the ‘show’ function presents the plot.

Creating a confidence interval plot in Matplotlib is a convenient way to visually analyze your data, especially data that involves statistical analysis. This powerful tool offers an easy and intuitive way to present complex data in a form which can be easily interpreted, making it an essential toolkit for any python data analyst or scientist. By understanding how to manipulate and use this, we can make the process of data interpretation more efficient and accurate.

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