I am trying to fit data into a skew normal distribution using the SciPy Skewnorm package.
However, I am failing to understand the usage properly as I cannot find proper documentation or examples on this matter.
On the help section I found Documentation and trying to use skewnorm.fit()
along with skewnorm.pdf()
to fit data into a model and use that model to output a distribution and compare with the original data.
Please let me know if anyone can help with this.
from scipy import stats
import matplotlib.pyplot as plt
import numpy as np
# choose some parameters
a, loc, scale = 5.3, -0.1, 2.2
# draw a sample
data = stats.skewnorm(a, loc, scale).rvs(1000)
# estimate parameters from sample
ae, loce, scalee = stats.skewnorm.fit(data)
# Plot the PDF.
plt.figure()
plt.hist(data, bins=100, normed=True, alpha=0.6, color='g')
xmin, xmax = plt.xlim()
x = np.linspace(xmin, xmax, 100)
p = stats.skewnorm.pdf(x,ae, loce, scalee)#.rvs(100)
plt.plot(x, p, 'k', linewidth=2)
Output:
To calculate the sample skewness and sample kurtosis of this dataset, we can use the skew() and kurt() functions from the Scipy Stata librarywith the following syntax: skew(array of values, bias=False) kurt(array of values, bias=False)
skewnorm takes a real number as a skewness parameter When a = 0 the distribution is identical to a normal distribution ( norm ). rvs implements the method of [1]. The probability density above is defined in the “standardized” form. To shift and/or scale the distribution use the loc and scale parameters.
Pandas DataFrame skew() Method The skew() method calculates the skew for each column. By specifying the column axis ( axis='columns' ), the skew() method searches column-wise and returns the skew of each row.
The function skewtest can be used to determine if the skewness value is close enough to zero, statistically speaking.
Here is an example to get you started.
>>> from scipy import stats
# choose some parameters
>>> a, loc, scale = 1.3, -0.1, 2.2
# draw a sample
>>> sample = stats.skewnorm(a, loc, scale).rvs(1000)
# estimate parameters from sample
>>> ae, loce, scalee = stats.skewnorm.fit(sample)
>>> ae
1.2495366661560348
>>> loce
-0.039775813819310835
>>> scalee
2.1126121580965536
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