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From |
n j cox <n.j.cox@durham.ac.uk> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: RE: sub-dataset by variable numbers |

Date |
Tue, 02 Oct 2007 19:22:27 +0100 |

Sebastian showed a good way to do this, but I agree with Seyi.

It is to me easier (and perhaps less error-prone) to select by names, than to map variable names to numbers and work with those. I'd be interested to hear the context in which working with numbers appears

more natural (or more convenient) than working with names.

Thanks to Seyi for the plug for -renames-. -renames-

remains on SSC because it might be useful to any people

still on Stata 6 [sic]. Those using Stata 7 will be

better off using -renvars- from STB-60 and those

using Stata 8 up will be better off using -renvars-

from SJ 5(4). I'll ask Kit Baum to amend the package description

so that this is clearer.

Nick

n.j.cox@durham.ac.uk

Jian'an Luan asked

I wonder if I can select a sub-dataset by variables without given

variable names but using variable numbers, something like the command

when select a sub-dataset by observations ".keep if _n>1001 & _n<2000".

Sebastian Buechte replied

I do not think there is a direct command which will help you to

achieve what you would like. But, you could try the following:

unab vlist : _all

//keep 3rd to 6th variable from dataset in memory

keep `: word 3 of `vlist'' - `: word 6 of `vlist''

This will read all variable names into a local macro (vlist) and then

uses local extended functions to extract numbered elements from this

macro. For more information look at: -help unab- and -help

extended_fcn-

Seyi Soremekun replied

I don't think Stata will allow variable names starting with numbers.

But if you want your list of variables in some kind of number-related

format, maybe you could rename all your variables as a series such as

A1, A2...etc...

You can do this en masse using Nick Cox's 'renames' programme code:

http://ideas.repec.org/c/boc/bocode/s388102.html

e.g renames price-age \ a1-a20 (if you have 20 different variables with

the first being 'price' and the last being 'age')

then you can use 'drop' or 'keep' to remove part of the dataset

drop a1-a12

But I'm sure you can do this anyway without having to rename your

variables (e.g. drop price-year), so you only need to use the -renames-

command if you really want to convert your variable names into some kind

of numerical-like list.

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**Follow-Ups**:**RE: st: RE: sub-dataset by variable numbers***From:*"Jian'an Luan" <jal42@medschl.cam.ac.uk>

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