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MathGroup Archive 2007

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Re: averaging sublists of different lengths

  • To: mathgroup at smc.vnet.net
  • Subject: [mg75506] Re: averaging sublists of different lengths
  • From: dh <dh at metrohm.ch>
  • Date: Thu, 3 May 2007 03:49:19 -0400 (EDT)
  • References: <f19fql$4q7$1@smc.vnet.net>


Hi,

to get the mean of the i_th values, we first extract all rows with at 

least i elements:

Cases[t1,x_/;Length[x]>=#],

  and get the i-th element:Part[..,All,#]

  We apply the "Mean" to the resulting list. This we do for all i. 

Everything together, assuming the list is in "d":

Mean@Part[Cases[d,x_/;Length[x]>=#],All,#]&/@Range[Max@Length@d]

hope this helps, Daniel





dantimatter wrote:

> Hello all,

> 

> I have a list of lists like this:

> 

> {{70, 66, 64, 68, 64, 56, 68, 78, 62, 68, 84}, {70, 64, 64, 56, 66,

> 56, 62,

>     64, 66, 88, 54, 72}, {58, 54, 54, 60, 72, 70, 62, 68, 74, 76, 70},

> {66,

>     56, 60, 64, 56, 62, 68, 58, 58, 58, 68, 76, 62, 76, 66, 64, 88,

> 56}, {56,

>     64, 72, 72, 70, 62, 76, 76, 76, 76, 86, 80, 100}, {60, 60, 70, 68,

> 60, 60,

>      50, 56, 60, 70, 62, 68, 88, 84, 82}, {54, 66, 72, 62, 70, 66,

> 70,

>     56}, {60, 60, 60, 62, 74, 80, 70}, {54, 62, 64, 72, 76, 74}, {66,

> 74, 70,

>     80, 54, 54, 64}, {72, 66, 60, 52, 52, 66, 66, 58, 60, 66}}

> 

> What I'd really like is the average all the 1st values, 2nd values,

> etc, but I'm having trouble figuring out how to deal with the fact

> that the lists are not all the same length.   Is there a way to drop

> the sublists as they run out of points to add to the average, i.e. if

> I want the average of all the nth values, but Length[shortSublist] <

> n, can I somehow drop shortSublist and then calculate the average from

> the other sublists?

> 

> Also, the Mean[] function requires more than one data point, but I'd

> still like to extract out the values for which there is only one data

> point.  Is there a way to do this?

> 

> Thanks!

> dan

> 

> 




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