Draw the density curve exactly on the Histogram without normalizing

Question

I need to draw the density curve on the Histogram with the actual height of the bars (actual frequency) as the y-axis.

Try1: I found a related answer here but, it has normalized the Histogram to the range of the curve.

Below is my code and the output.

import numpy as np
import matplotlib.mlab as mlab
import matplotlib.pyplot as plt
from scipy.stats import norm

data = [125.36, 126.66, 130.28, 133.74, 126.92, 120.85, 119.42, 128.61, 123.53, 130.15, 126.02, 116.65, 125.24, 126.84,
        125.95, 114.41, 138.62, 127.4, 127.59, 123.57, 133.76, 124.6, 113.48, 128.6, 121.04, 119.42, 120.83, 136.53, 120.4,
        136.58, 121.73, 132.72, 109.25, 125.42, 117.67, 124.01, 118.74, 128.99, 131.11, 112.27, 118.76, 119.15, 122.42,
        122.22, 134.71, 126.22, 130.33, 120.52, 126.88, 117.4]
(mu, sigma) = norm.fit(data)
x = np.linspace(min(data), max(data), 100)

plt.hist(data, bins=12, normed=True)
plt.plot(x, mlab.normpdf(x, mu, sigma))

plt.show()

Try2: There @DavidG has given an option, a user defined function even it doesn't cover the density of the Histogram accurately.

def gauss_function(x, a, x0, sigma):
    return a * np.exp(-(x - x0) ** 2 / (2 * sigma ** 2))
test = gauss_function(x, max(data), mu, sigma)

plt.hist(data, bins=12)
plt.plot(x, test)
plt.show()

The result for this was, But the actual Histogram is below, where Y-axis ranges from 0 to 8, And I want to draw the density curve exactly on that. Any help this regards will be really appreciated.

score 3 · Accepted Answer · answered Jul 05 '18 at 07:28

Is this what you're looking for? I'm multiplying the pdf by the area of the histogram.

import numpy as np
import matplotlib.pyplot as plt
from scipy.stats import norm

data = [125.36, 126.66, 130.28, 133.74, 126.92, 120.85, 119.42, 128.61, 123.53, 130.15, 126.02, 116.65, 125.24, 126.84,
        125.95, 114.41, 138.62, 127.4, 127.59, 123.57, 133.76, 124.6, 113.48, 128.6, 121.04, 119.42, 120.83, 136.53, 120.4,
        136.58, 121.73, 132.72, 109.25, 125.42, 117.67, 124.01, 118.74, 128.99, 131.11, 112.27, 118.76, 119.15, 122.42,
        122.22, 134.71, 126.22, 130.33, 120.52, 126.88, 117.4]

(mu, sigma) = norm.fit(data)
x = np.linspace(min(data), max(data), 100)

values, bins, _ = plt.hist(data, bins=12)
area = sum(np.diff(bins) * values)

plt.plot(x, norm.pdf(x, mu, sigma) * area, 'r')
plt.show()

Result:

Yes. That's what I wanted. Thanx a lot for your effort. – Surani Matharaarachchi Jul 05 '18 at 08:19 — Surani Matharaarachchi, Jul 05 '18 at 08:19

Draw the density curve exactly on the Histogram without normalizing

1 Answers1