Converting two lists into a matrix

Question

I ll try to be as clear as possible  and I ll start by explaining why I want to transform two arrays into a matrix   To plot the performance of a portfolio vs an market index I need a data structure like in this format     portfolio value1  index value1    portfolio value2  index value2     But I have the the data as two separate 1-D arrays   portfolio    portfolio value1  portfolio value2       index    index value1  index value2         So how do I transform the second scenario into the first  I ve tried np insert to add the second array to a test matrix I had in a python shell  my problem was to transpose the first array into a single column matrix   Any help on how to achieve this without an imperative loop would be great

User · Answer

Simple you can try this a list zip portfolio  index

User · Answer

Assuming lengths of portfolio and index are the same   matrix      for i in range len portfolio        matrix append  portfolio i   index i      Or a one-liner using list comprehension   matrix2     portfolio i   index i   for i in range len portfolio

User · Answer

The standard numpy function for what you want is np column stack    gt  gt  gt  np column stack   1  2  3    4  5  6    array   1  4           2  5           3  6      So with your portfolio and index arrays  doing  np column stack  portfolio  index     would yield something like     portfolio value1  index value1     portfolio value2  index value2     portfolio value3  index value3

User · Answer

You can use np c   np c   1 2 3    4 5 6    It will give you   np array   1 4    2 5    3 6

[python] Converting two lists into a matrix

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