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Re: List Manipulation- Advanced beginner question

• To: mathgroup at smc.vnet.net
• Subject: [mg121494] Re: List Manipulation- Advanced beginner question
• From: Sseziwa Mukasa <mukasa at gmail.com>
• Date: Sat, 17 Sep 2011 06:26:47 -0400 (EDT)
• Delivered-to: l-mathgroup@mail-archive0.wolfram.com
• References: <201109160948.FAA12399@smc.vnet.net>

On Sep 16, 2011, at 5:48 AM, Nguyen Van Falk wrote:

> I am trying to add multiple lists together and am looking for some
> guidance. My data is in the form of multiple time series, with dates
> that overlap one another. I need to merge the lists, add all of the
> values together  for the dates that overlap and output a single list
> that only has one entry for each date.
>
> For example, if I have three values for September 15 (8,14,10), I only
> want a single entry for September 15 in the final list with a value of
> 32. The data is in standard date spec form: { {{Date 1}, Value 1},
> {{Date 2}, Value 2},  {{Date 3}, Value 3}, ....... {{Date n}, Value
> n}, }.

My approach would be to sort the lists together, use Split to group the 
items with the same date together, then map a function over the result 
which sums up the elements in the list, for example (be warned this code 
is untested but should give you the general idea):

Total/@Split[Sort[Join[series1,series2,...]]]

Regards,
	Ssezi

• References:
  • List Manipulation- Advanced beginner question
    • From: Nguyen Van Falk <nvanfalk@gmail.com>