Re: Basic Stat Question
- To: mathgroup at smc.vnet.net
- Subject: [mg42633] Re: Basic Stat Question
- From: Bill Rowe <listuser at earthlink.net>
- Date: Fri, 18 Jul 2003 05:25:32 -0400 (EDT)
- Sender: owner-wri-mathgroup at wolfram.com
On 7/17/03 at 3:45 AM, Moranresearch at aol.com wrote:
> I have a list l1= {{xi,yi}}
> I want to find the Mean xi where s <y < t
> for a series of s and t.
If you are using Mathematica 5.0 then
Mean[First/@Select[list, (s < Last@# && Last@# < t)&]]
will do what you want. If you are using a version earlier than 5.0 you will need to define the function Mean or load the package Statistics`DescriptiveStatistics`
> So say I have the height of a million children and I want to know the average
> height at age 1, 2, 3...18. How do I do this?
> Also the data a field "Gender" how do I select the subset "Girls" or "Boys"
> to analyze.
The answers to these depend on how you have organized your data. Suppose you have the data organized as a list of items structured as {height, age, gender} where height and age are numbers and gender is a string.
Then
Mean[First/@Select[data, #[[2]]==18&]]
will compute the average height at age 18
and
Mean[First/@Select[data,StringMatchQ[Last@#, "Girl"]&]]
will compute the average hieght of girl.