Plotting an average

Question

I want to plot an average of 24 arrays, but had an error message ''list' object has no attribute 'shape''. Where's the mistake?

empty_array=numpy.zeros[2,30,100]
for x in range (1,25):
    array = array[x,:,:,:]
    empty_array += array
average = map(lambda x:x/24,empty_array)

plt.figure(1)
plt.pcolor(average)
plt.colorbar(orientation='horizontal')                 

Answer 1

It looks like you want to compute the average in one of the axis. You can simply use np.mean() for this. Example from docs:

>>> a = np.array([[1, 2], [3, 4]])
>>> np.mean(a)
2.5
>>> np.mean(a, axis=0)
array([ 2.,  3.])
>>> np.mean(a, axis=1)
array([ 1.5,  3.5])

The key here is to correctly define the axis you want to average over.

Other mistakes:

• np.zeros() take a tuple describing the shape as an input, i.e. np.zeros((2,30,100)).
• The reason you get "'list' object has no attribute 'shape'" is that average is a python list. Lists in python has no attribute named shape. plt.pcolor() expect a 2-D (numpy) array.

Answer 2

empty_array=[2,30,100] does not create an empty array. It is a list containing three numbers. You are looking for numpy.zeros