Question

I am trying to plot a lognormal distribution so I can compare it with a histogram of my sample data using the code below but my plot does not look right. Is there something with my code that I am not doing correctly?
The C array has a length of 17576

import matplotlib.pyplot as plt
import numpy as np

data=np.loadtxt(F)
C=data[:,3]

x = np.ma.log(C)
avg = np.mean(x)
std = np.std(x)
dist=lognorm(std,loc=avg)
plt.plot(C,dist.pdf(C),'r')
plt.show()

Answer 1

It looks like your x data are not in sorted order. Try this

ind = np.argsort(C)
xx = C[ind]
yy = dist.pdf(C)[ind]
plt.plot(xx, yy, 'r')

Plot just connects all the (x,y) pairs with straight lines, so you need to make sure you trace your function from left-right (or right-left). Alternatively, you can skip the lines between the plot:

plt.plot(C, dist.pdf(C), 'ro')