split Joinnode outputs list of lists

[thomas.nickson]

Hi All,

I use a joinnode in my code (https://gist.github.com/thelxinoe/4df88d01a60967a7e331) to collate results before doing a group ICA over subsets of the input formed by a split node. When I do this instead of getting a list as the output of the split function I get a list of lists and I can't use this as the input to the ica. Is there anyway to specify the out of the split node or what's the easiest way to collapse the lists in to one. Could I use a function node and normal python list functions?

Thanks,

Tom

[Satrajit Ghosh]

hi tom,

are you trying to run ica on both parts of the split or just on one part?

if both, then the next part would probably be a mapnode.

if one part, you could do something as trivial as:

select_split = lambda x, y: return x[y]

or 

def select_split(listoflists, index):

    return listoflists[index]

wf.connect(myjoinnode, ('output', select_split, 0), nextnode, 'input')

cheers,

satra

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[thomas.nickson]

I have the split function in the join node so that I can now access the splits with out1 or out2 etc but they are lists of lists. If I want to access the first three of a [3,3,3] split with out1 then I get [[1],[1],[1]] but the ICA wants just one list that contains [1,1,1].

I think can modify your example of a function node to collapse the list in to one list but the result of the split struck me as a bit odd in general. I'm not sure how useful it is to do it this way. If I have a list of inputs then it's easy to map or iterate over them but this way, a list of lists, I need to write a custom function to get the result that I want.

Thanks,

Tom