Question

So I’d like to plot simple gamma function, but I have some problems. My code is:

#!/usr/bin/env python
# -*- coding: cp1250 -*-
#import math
from scipy.special import *
#from scitools.std import *
from pylab import *

def f1(x):
    return gamma(x)


x = linspace(-6, 6, 512)
y1 = f1(x)

# Matlab-style syntax:
plot(x, y1)

xlabel('x')
ylabel('y')
legend(r'$\Gamma(x)$')
grid(True)

show()

I tried importing the gamma function from math, and from scipy.special but I get the following error:

Traceback (most recent call last): File “D:/faxstuff/3.godina/kvantna/plotgamma.py”, line 13, in y1 = f1(x) File “D:/faxstuff/3.godina/kvantna/plotgamma.py”, line 9, in f1 return gamma(x) File “mtrand.pyx”, line 1599, in mtrand.RandomState.gamma (numpy\random\mtrand\mtrand.c:8389) ValueError: shape <= 0

How to do it? This should be easy, but I seem to fail 🙁

Answer 1

One of the modules (pylab, I think) is shadowing the gamma function by the gamma random variable function. This works, but I had to turn off the call to legend (I’m not sure why, yet).

from scipy.special import gamma as Gamma
#from scitools.std import *
from pylab import *

def f1(x):
    return Gamma(x)


x = linspace(-6, 6, 512)
y1 = f1(x)
gca().set_autoscale_on(False)

# Matlab-style syntax:
plot(x, y1)

xlabel('x')
ylabel('y')
# legend(r'$\Gamma(x)$')
axis([-6, 6, -100, 100])
grid(True)

show()