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Re: st:How to input a portion of a file


From   Joseph Wagner <joseph.wagner@wright.edu>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st:How to input a portion of a file
Date   Thu, 21 Feb 2008 11:23:21 -0500

As Friedrich pointed out, Stata does import the columnar data quite well and deleting the first lines of the 'header' region will work - to a point. I do have a single line of data that I need from the header area. I would be happy to send the ascii text file as well as the excel spreadsheet that has the needed variables highlighted if anyone is interested in getting a better look.

Sergiy Radyakin wrote:

Stata does not "guess". Stata determines the variable types using a
"scientific method of looking". Stata looks not "at the early bit of
the file" - it looks at the whole file. This is called "the first
pass". After the variable types are determined - the file can be read
in - that is called "the second pass". Users of StatTransfer will be
familiar with this technique - StatTransfer will do two passes over
your data and is very explicit at showing it's progress.

It remains unclear, however, what the third pass in the Stata's
-insheet- procedure is for. It could be a simple ineffeciency of code,
or it could be something else, which I don't see at the moment, which
necessitates the third pass (and this is more probable, since even the
most recent version does so).

The fact is however, that Stata will fully read the file 3 times when
importing from text format. If the file is already in dta format, one
pass is enough, and here Stata is very fast.

Best regards,
Sergiy Radyakin



On 2/21/08, Nick Cox <n.j.cox@durham.ac.uk> wrote:

That's an instructive example.

As I understand it, -insheet- peeks at the early bit of the file, makes
a guess at the number and type of variables, and assigns accordingly.
Whether guessing will also reliably give a workable answer with Joseph
Wagner's files, I can't say.

Nick
n.j.cox@durham.ac.uk

Friedrich Huebler

Assume we have a file "test.txt" that contains the following text
(without the Start and End lines). We are only interested in the
numbers.

=== Start of file ===
I am not clear how that this will help, as the header text and
the remainder of the file will give -insheet- quite different
ideas about what variables there are.
mpg trunk turn
22 11 40
17 11 40
22 12 35
20 16 40
=== End of file ===

Let's import the data with -insheet-.

. insheet using test.txt, nonames delimiter(" ")
(14 vars, 8 obs)
. drop if _n < 5
(4 observations deleted)
. drop v4 - v14
. list

+--------------+
| v1 v2 v3 |
|--------------|
1. | 22 11 40 |
2. | 17 11 40 |
3. | 22 12 35 |
4. | 20 16 40 |
+--------------+

Friedrich

On Wed, Feb 20, 2008 at 6:35 AM, Nick Cox <n.j.cox@durham.ac.uk> wrote:

I am not clear how that this will help, as the header text and the
remainder of the file will give -insheet- quite different ideas about
what variables there are.


Nick
n.j.cox@durham.ac.uk

Friedrich Huebler


You wrote that -insheet- with subsequent deletion of unwanted data is
"sloppy". That approach might still be the easiest if all files have
the same structure and your data always appear in the same columns.

. insheet using filename, nonames
. drop if _n < 30 | _n > 129
. drop v1 - v20 v25 - v30



On Feb 18, 2008 9:26 AM, Joseph Wagner <joseph.wagner@wright.edu>
wrote:

> I have data I wish to input a portion of into STATA. Data is
collected
> on patients by a machine that measures their gait as they walk. A
text
> file is output for each patient with columns representing variables
> (each about 130 lines long) but the multiple observation data
doesn't

> start until line 29. The first 28 lines are taken up with short
lines

> of data describing the patient. Unfortunately, I also need a
couple

of
> those lines in 'header' area. The 29th line has the variables
names

but
> they do not line up directly with the columns of data so I figured
I

> could just label the data later. The data I need starts 30 lines
down

> at column 115 and includes the next 4 columns and goes down 100
lines.

>
> I realize there are easier ways to do this but I have data on about
300
> patients (and so one file for each person) and wanted to automate
this

> input (followed by successive merging of files to get my final
dataset).
>
> I wanted to use the -infix- command but have never used this
command

> before and my attempts so far have failed. I also tried using
-infile-
> with the _first(30) option and the _line(30) option but those
didn't

> seem to work either.
>
> Here is a dictionary I attempted with just one of the variables:
>
> dictionary using "c:\data\gait\SBS00001_20050607_1.nrm" {
> _line(30)
> _column(115) r_grf_vrt_frc %5f
> }
>
> infile using SBS00001_20050607_1.dct
>
> unexpected end of file
> (5 observations read)
>
> The other problem is that it didn't seem to pull the data
corresponding
> to that column. I thought perhaps there was a problem with the
data

not
> being in a fixed format but if I try -insheet- all the data imports
and
> the correct data lines up in the individual columns. Of course I
could
> write some programming whereby I delete the unneeded variables and
line
> but that's kind of sloppy.
>
>
>
> I am using STATA ver. 8.2
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--
Joseph H. Wagner, M.P.H.
Lifespan Health Research Center
Wright State University Boonshoft School of Medicine
3171 Research Blvd.
Kettering, OH 45420-4014

(937) 775-1494 (LHRC office)
(937) 775-1456 (fax)

joseph.wagner@wright.edu

Visit the Lifespan Health Research Center Home Page at:
http://www.med.wright.edu/lhrc
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