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Re: st: How do we access instream data (other than -input- and -display _request-)?
From
"Roger B. Newson" <[email protected]>
To
[email protected]
Subject
Re: st: How do we access instream data (other than -input- and -display _request-)?
Date
Mon, 06 Jan 2014 20:23:17 +0000
Sorry, -_request()- should have been -_request2()- in my last message.
And I have done some experiments, and -_request2()- seems to keep
interrogating the terminal after it finds the ed of a do-file, whether
the do-file is delimited by cr or ;.
So, is there a way of detecting the end of a do-file? (As the -input-
command seems to do.)
Best wishes (and thanks in advance)
Roger
Roger B Newson BSc MSc DPhil
Lecturer in Medical Statistics
Respiratory Epidemiology, Occupational Medicine
and Public Health Group
National Heart and Lung Institute
Imperial College London
Royal Brompton Campus
Room 33, Emmanuel Kaye Building
1B Manresa Road
London SW3 6LR
UNITED KINGDOM
Tel: +44 (0)20 7352 8121 ext 3381
Fax: +44 (0)20 7351 8322
Email: [email protected]
Web page: http://www.imperial.ac.uk/nhli/r.newson/
Departmental Web page:
http://www1.imperial.ac.uk/medicine/about/divisions/nhli/respiration/popgenetics/reph/
Opinions expressed are those of the author, not of the institution.
On 06/01/2014 19:48, Roger B. Newson wrote:
Thanks to Alan for this very helpful response.
One immediate query. What happens when -_request()- finds the end of a
do-file? Does it keep on requesting from the terminal? Or is there a way
of using it to detect the end of the do-file, and terminating the
request sequence automatically?
Best wishes (and thanks in advance)
Roger
Roger B Newson BSc MSc DPhil
Lecturer in Medical Statistics
Respiratory Epidemiology, Occupational Medicine
and Public Health Group
National Heart and Lung Institute
Imperial College London
Royal Brompton Campus
Room 33, Emmanuel Kaye Building
1B Manresa Road
London SW3 6LR
UNITED KINGDOM
Tel: +44 (0)20 7352 8121 ext 3381
Fax: +44 (0)20 7351 8322
Email: [email protected]
Web page: http://www.imperial.ac.uk/nhli/r.newson/
Departmental Web page:
http://www1.imperial.ac.uk/medicine/about/divisions/nhli/respiration/popgenetics/reph/
Opinions expressed are those of the author, not of the institution.
On 06/01/2014 17:30, Alan Riley wrote:
Roger Newson asked whether it is possible for a program to
read instream data much in the way the -input- command does.
That is, if a program needs to ask a question, Roger would like
the response to be obtained interactively from the user (if the
program was called by the user interactively) OR from the next line
or lines in the do-file (if the program was called by a do-file):
During the Wishes and Grumbles session of the 2013 UK Stata User
Meeting, I recall asking if there was a way, in Stata, of reading
instream data, in the way that the -input- command does. That is to
say, I wanted to write ado-files so that they could read in the next
few lines of input, either from the Command window (if the ado-file
was invoked interactively from the Command window), or from the next
few lines of the do-file (if the ado-file was invokedfrom a
do-file). Of course, you can do something similar to this by
including an -input- command in your ado-file, but then the string
values you input must either be words or be quoted. I would prefer
to be able to input lines of text from a do-file, and worry about
words and/or quotes afterwards. And the -display _request- facility,
as I understand, does not do this, either, but just sends input
requests to the console. I was advised that there was a way to do
what I wanted to do, but that it was not officially publicized.
I have looked under -help undocumented- in my Stata/MP Version 13,
but have not found anything that looks like such a capability. Maybe
I was not looking hard enough. And maybe this capability is so
unpublicized that it is not even mentioned in -help undocumented-.
But does such a capability exist?
Such a capability does exist, but is not even undocumented
(mentioned in -help undocumented-); it is not documented.
This not-documented facility is a twist on the -_request()- directive
of the -display- command. Roger already knows about -_request()-
For those of you who don't, you can read about it in [P] display, and
I'll also describe it briefly here. If I were to code
display _request(somemacroname)
then Stata would display a dot prompt and wait for me to type
something. Whatever I typed would go in the global macro
"somemacroname" and I could refer to it later with "$somemacroname".
Usually Stata programmers want the result to go into a local macro name,
which is possible merely by prepending an underscore when specifying
the macro name with -_request()-,
display _request(_somemacroname)
and the contents of the local macro can then be accessed as
"`somemacroname'".
It matters not whether -_request()- is used interactively, in
a do-file, or in a program (ado-file). It always displays an interactive
dot prompt and waits for the user to type something. It does this
even if the ado-file in which -_request()- occurs is called by
a do-file! -_request()- skips right over the do-file and goes back to
the interactive session to get the response.
What Roger wants though, is not to skip over the do-file, but
to get the response from the do-file, just as -input- would.
-display _request2()- can do that. Here is a simple example. Assume
the following program is defined in myexample.ado:
program myexample
display "hello from myexample"
display "let's get some text:"
display _request2(_mymacro)
display `"I got |`mymacro'|."'
display "goodbye from myexample"
end
If I call -myexample- interactively, I will see something like
. myexample
hello from myexample
let's get some text:
.
Stata is now waiting for me to type something. I'll type
"this is a test", hit enter, and see what happens:
. myexample
hello from myexample
let's get some text:
. this is a test
I got |this is a test|.
goodbye from myexample
Great -- I typed "this is a test", it was placed into the
local macro "mymacro" within my -myexample- program, and
that was displayed.
If instead I call -myexample- from a do-file, I can put
anything I want in the do-file on the line immediately after
the call to -myexample-, and -display _request2()- will read
it from the do-file rather than asking me to enter it
interactively. If I put the following lines in a do-file,
myexample
this is a test
myexample
this is another test
and then execute that do-file, I will see
. myexample
hello from myexample
let's get some text:
. this is a test
I got |this is a test|.
goodbye from myexample
. myexample
hello from myexample
let's get some text:
. this is another test
I got |this is another test|.
goodbye from myexample
Alan
[email protected]
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