Gamma random numbers, MATLAB and Python

Question

I have this line of code in a MATLAB program:

x(:,i) = gamrnd(a(i),1,dim,1)

I was wondering in what way I could write this same line in Python. I think the equivalent statement is:

gamma.rvs(a, size=1000)

However, this keeps giving me an Index Error.

Here is my full code for this part:

x = np.array([])
for i in range(N-1):
    # generates dim random variables
    x[:, i] = gamma.rvs(a[i], dim-1)    # generates dim random variables
                                            # with gamma distribution

Thanks for the help!

Please post the actual error you're seeing and when it occurs. gamma.rvs(a, size=1000) should just work. — Horia Coman
– Horia Coman, Commented Aug 17, 2018 at 21:55

Zain Patel · Accepted Answer · 2018-08-17 22:03:38Z

0

You initialized x = np.array([]) and then tried accessing x[:, 0], which doesn't exist, hence the Index Error. You'll want to append instead:

x = np.array([])
for i in range(N-1):
    np.append(x, gamma.rvs(a[i], dim - 1))

The documentation for np.append can be found here.

answered Aug 17, 2018 at 22:03

Zain Patel

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1 Comment

user2357112 Over a year ago

np.append is extremely inefficient. Also, this will produce a flat array rather than the shape the questioner is looking for.

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