Merge 2D list of masked arrays with different lengths

Question

I have a very large list of masked arrays, which I want to combine together, but the arrays have different lengths. To keep it simple this is what I want to do, I want to obtain C:

A=[[--,--,--,...,--]
   [1,2,3,...,--,--],
   ...
B=[[--,--,--,...,--],
   [4,5,6,...,--,--],
   ...
C=A+B
C=[[--,--,--,...,--,--,--,--,...,--],
   [1,2,3,...,--,--,4,5,6,...,--,--],
   ...
len(A)= 81
len(B)= 81
len(A[0])=2700
len(B[0])= 5000

len(C) = 81
len(C[0])= 7700

So I'm basically just putting the two lists next to each other. In reality, my array A looks like this (B is similar):

masked_array(
  data=[[--, --, --, ..., --, --, --],
    [--, --, --, ..., --, --, --],
    [--, --, --, ..., --, --, --],
    ...,
    [-3.6872851848602295, -3.732004165649414, -3.7555367946624756,
     ..., -3.8215177059173584, -3.7747914791107178,
     -3.819281816482544],
    [-3.819749116897583, -3.824702739715576, -3.804812431335449, ...,
     -3.863957643508911, -3.840423345565796, -3.8660500049591064],
    [-3.6894078254699707, -3.7181897163391113, -3.7022457122802734,
     ..., -3.8167803287506104, -3.7095720767974854,
     -3.8254523277282715]],
  mask=[[ True,  True,  True, ...,  True,  True,  True],
    [ True,  True,  True, ...,  True,  True,  True],
    [ True,  True,  True, ...,  True,  True,  True],
    ...,
    [False, False, False, ..., False, False, False],
    [False, False, False, ..., False, False, False],
    [False, False, False, ..., False, False, False]],
  fill_value=9.96921e+36,
  dtype=float32)

The problem is that most commands don't work either because it's a masked array or because it has different sizes. I already checked these questions:

• merge 2D array into a list python
• merging two lists, removing empty strings

Any help is appreciated!

Answer 1

One option is to use the usual numpy operations on the data and mask separately:

c_data = np.hstack((a.data, b.data))
c_mask = np.hstack((a.mask, b.mask))
c = ma.array(c_data, mask=c_mask)