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Re: Select, from table data

  • To: mathgroup at smc.vnet.net
  • Subject: [mg112993] Re: Select, from table data
  • From: "Nasser M. Abbasi" <nma at 12000.org>
  • Date: Sun, 10 Oct 2010 06:41:20 -0400 (EDT)
  • References: <i8pgih$fjn$1@smc.vnet.net>
  • Reply-to: nma at 12000.org

On 10/9/2010 3:36 AM, Kurtis wrote:
> Easy fix here.
>
> I'm trying to drop outliers from 2D data originally collected in the
> time domain.  My method is to analyze the 2nd derivative of smoothed
> data and drop those deviating more than, say 3x the standard deviation
> from the mean. I need to make a new table of the smoothed data with
> these outliers dropped.  I'm attempting the Select function in the
> last line, i'm just not familiar enough with the syntax for analyzing
> the criteria in the 2nd column (y values) from the dataset.  Thanks!
>
> SetDirectory[NotebookDirectory[]];
> set = Import ["testMELT2.xls", {"Data", 1}];
> <<  Smooth` (* savitzsky-golay - like filter *)
>
> t = Table[set[[n]][[1]], {n, 1, Length[set]}];

I am a little confused (not too much xls exposure), but it seems to me 
that you have just imported one sheet (the first one), so set is just a 
matrix. So to get the first column, why not just write


t=set[[All,1]]

?

> a260 = Table[set[[n]][[2]], {n, 1, Length[set]}];

a260=set[[All,2]]

?


> Dataset1 = Table[{t[[n]], a260[[n]]}, {n, 1, Length[set]}];
>


Dataset1=t[[All,1;;2]]

?

(I'll leave the rest for someone else to figure out for now :)

>
> SmoothDatasetDERIV = Smooth[Dataset1, 13, 3, 2]; (* external package
> filtering over 13 points, polynomial order 3, f'')
> meanSECderiv = Mean[SmoothDatasetDERIV];
> meanY = meanSECderiv[[2]]  (* pulling out Y values *)
> sd = StandardDeviation[SmoothDatasetDERIV];
> sdY = sd[[2]]  (* pulling out Y values *)
>
> revision =
>   Select[{SmoothDatasetDERIV}, Function[Abs[meanY - #<= (3*sdY)&]]]
>
>
>
> Any help would be great, thanks!
>
>


--Nasser


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