       Re: Mathematica function writing for data analysis at Gould Academy

• To: mathgroup at smc.vnet.net
• Subject: [mg35742] Re: Mathematica function writing for data analysis at Gould Academy
• From: Peter <petsie at arcor.de>
• Date: Sun, 28 Jul 2002 03:32:24 -0400 (EDT)
• References: <ahr0u6\$l2l\$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```Charles H. Dresser wrote:
> Hello,
> I work at Gould Academy and have recently taught myself some of the
> Mathematica scripting language. It has been my job to write functions
> which will make analyzing data in Mathematica simpler for the
> students. I have written a number of scripts which find different
> regressions of data within a file easily. But, a couple of the
> functions that I have written are not doing exactly what I want them
> to do. One of them takes the input from a file with multiple columns
> and what number columns the user wants to be included in the data as
> ordered pairs and is suppose to output the ordered pairs which was
> selected. What it does is it doesn't output anything but does set list
> equal to the data which it should output.  This is the code I have
> written (Sorry If It Is Ugly):
>
> f is a filename x is the column which is wanted to be the x value in
> the order pairs y is the y value which is wanted to be the ordered
> pairs.
>
>   MultCol[f_, x_, y_] :=
>   Do[For[i = 1; list = {}; length = Length[Import[f, "Table"]], i <=
> length,
>         i++,
>         list =
>           Append[list, {Part[Part[Import[f, "Table"], i], x],
>               Part[Part[Import[f, "Table"], i], y]}]]
> MultColCleanUp[], {1}]
>
> MultColCleanUp[] :=
>   If[DigitQ[StringTake[ToString[First[list]], {2}]], list = list,
>     list = Rest[list]]
>(...)

MultCol[f_,x_,y_]:=
Select[ Import[f, "Table"][[All, {x, y}]], NumberQ[First[#]]& ]
should work.

If you want to keep your Functions, you should consider using local variables:
MultCol[f_,x_,y_]:=Module[{list,i}, Do[...]; list]
but in my opinion it is bad style (sorry), to read the file 2*length times.
To assign the result to the global variable list do:
list = MultCol[f,2,5].

Regards,
Peter
--
u will c how to mail me...

```

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