Page 203 - Robotics and AI class 10
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●  Variance
                 It means how far each number in the given dataset is from the mean value. It is calculated as the average of the
               squares of the differences between an individual value and the expected value or average squared deviation of
               each number from the mean of a given data set.
               The formula for calculation:
                          2 ∑ ( x - µ) 2
                         σ
               variance =  =    r
                                n
               To calculate Variance in Python:

              import statistics
              marks=[45,34,41,46,47,39,38,48,45,34,41,39,39]
              m=statistics.variance(marks)
              print("the variance of marks :",round(m,2))
               Output:
               the variance of marks : 21.69

            Matplotlib
            Matplotlib was created by John D. Hunter in 2003. It is a free and open source, data visualisation library used for
            plotting graphs and visualisation in Python built on NumPy arrays and can be downloaded from https://www.
            matplotlib.org. Using Matplotlib, with just a few lines of code we can generate graphs of any kind like plots,
            histograms, bar charts, scatterplots, etc.
            It comes with a wide variety of plots but the most used module of Matplotib is Pyplot which is used for creating
            2D plots of arrays.
            Visuals have more impact on human brains. So these plots created using Matplotlib help us understand the trends,
            patterns, correlations of the data. They give us the quantitative information of data in a visual form. After the plots
            are created, you can change the style, look and make them more descriptive and communicable.
            Some types of graphs that we can make with this package are listed below:










                          Bar Graph        Histogram       Scatter Plot      Area Plot        Pie Plot
            Installing Matplotlib
               • To install it using pip:

               python -m pip install -U pip
              python -m pip install -U matplotlib
              Or
              pip install matplotlib
               • To install using Anaconda
              conda install matplotlib
              Or
              conda install -c conda-forge matplotlib
               For plotting using Matplotlib, we need to import its Pyplot module as follows:
               import matplotlib.pyplot as plt
                                                         Introduction to Data and Programming with Python  201
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