[python] Numpy `ValueError: operands could not be broadcast together with shape ...`

Im using python 2.7 and am attempting a forcasting on some random data from 1.00000000 to 3.0000000008. There are approx 196 items in my array and I get the error

ValueError: operands could not be broadcast together with shape (2) (50)

I do not seem to be able to resolve this issue on my own. Any help or links to relevant documentation would be greatly appreciated.

Here is the code I am using that generates this error

nsample = 50
sig = 0.25
x1 = np.linspace(0,20, nsample)
X = np.c_[x1, np.sin(x1), (x1-5)**2, np.ones(nsample)]
beta = masterAverageList
y_true = ((X, beta))
y = y_true + sig * np.random.normal(size=nsample)