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3 weeks ago - last edited 3 weeks ago

Hi, I have a data like this (sample data)

Group | Begdate | enddate |

A | 12-03-2005 | 25-08-2008 |

B | 03-06-2001 | 10-09-2003 |

C | 05-02-2011 | 21-06-2013 |

Now I want to have a variable "newdate" which is a random day between begdate and enddate. Also, this newdate has to be a weekday date (not saturday, sunday). Could anyone please show me how to do that? Thank you very much

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Posted in reply to trungcva112

3 weeks ago

There may be better ways, but here is something that works.

data all_weekdays;

set have;

original_record_num = _n_;

do day = begdate to enddate;

random_num = ranuni(12345);

if (2 <= weekday(day) <= 6) then output;

end;

run;

proc sort data=all_weekdays;

by original_record_num random_num;

run;

data want;

set all_weekdays;

by original_record_num;

if first.original_record_num;

drop original_record_num random_num;

format day mmddyyd10.;

run;

The variable DAY is the one that contains the randomly selected weekday.

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Posted in reply to Astounding

3 weeks ago

Hi. I tried your code, but each time I run it, it gave me the same day for each group. So the "day" is not random. How can we fix it?

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Posted in reply to trungcva112

3 weeks ago

Yes, the day is randomly selected. If you want it to select a different random day each time you run the program, change the seed to the random number generator, using:

ranuni(0)

However, once you do that you can never replicate your results. If asked to demonstrate that your results are correct, you will be unable to do so.

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Posted in reply to trungcva112

3 weeks ago

Are those dates sas-dates in your dataset?

From the documentation of the outdated (see https://blogs.sas.com/content/iml/2013/07/10/stop-using-ranuni.html) ranuni-function:

*The RANUNI function returns a number that is generated from the uniform distribution on the interval (0,1) [...]*

*You can use a multiplier to change the length of the interval and an added constant to move the interval. For example,*

random_variate=a*ranuni(seed)+b;

*returns a number that is generated from the uniform distribution on the interval (b,a+b).*

Because SAS-dates are numbers you can use begdate and enddate in the calculation. Replacing ranuni with rand('uniform') is recommended. The function weekday returns 1 for Sunday and 7 for Saturday, so you have to repeat calling rand-function until weekday returns 2-5.

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Posted in reply to andreas_lds

3 weeks ago

Hi. Yes it is SAS date (numeric format). I tried your method but there is always a weekend dates.

Now suppose I have a list of dates for each group (that already filter all weekends, holiday etc)

Group | Date |

A | 02-01-02 |

A | 03-01-02 |

A | 04-01-02 |

A | …. |

B | … |

B | … |

B | … |

B | … |

How can I pick 1 random date (random observation) for each group from this list. Is it easier to do?

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Posted in reply to trungcva112

3 weeks ago

@trungcva112 wrote:

Hi. Yes it is SAS date (numeric format). I tried your method but there is always a weekend dates.

Now suppose I have a list of dates for each group (that already filter all weekends, holiday etc)

Group Date A 02-01-02 A 03-01-02 A 04-01-02 A …. B … B … B … B …

How can I pick 1 random date (random observation) for each group from this list. Is it easier to do?

@Astounding does exactly this.

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Posted in reply to andreas_lds

3 weeks ago

But it gave me the same random date each time I run it

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Posted in reply to trungcva112

3 weeks ago

You will only get tested code when you supply example data against which the code can be tested. Post example data in a data step with datalines. A macro to convert existing datasets to data steps can be found here: https://communities.sas.com/t5/SAS-Communities-Library/How-to-create-a-data-step-version-of-your-dat...

How to post code: https://communities.sas.com/t5/Getting-Started/How-to-add-SAS-syntax-to-your-post/ta-p/224394

---------------------------------------------------------------------------------------------

Maxims of Maximally Efficient SAS Programmers

How to convert datasets to data steps

How to post code

Maxims of Maximally Efficient SAS Programmers

How to convert datasets to data steps

How to post code

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Posted in reply to trungcva112

3 weeks ago

See the documentation of ranuni, the same random numbers are generated if parameter seed is constant, to avoid this use 0, instead of 12345.

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Posted in reply to trungcva112

3 weeks ago

```
data have;
infile cards expandtabs;
input Group $ Begdate : ddmmyy10. enddate : ddmmyy10. ;
format Begdate enddate ddmmyy10. ;
cards;
A 12-03-2005 25-08-2008
B 03-06-2001 10-09-2003
C 05-02-2011 21-06-2013
;
run;
data want;
if _n_=1 then do;
declare hash h();
h.definekey('n');
h.definedata('date');
h.definedone();
end;
set have;
n=0;h.clear();
do date=begdate to enddate;
if weekday(date) not in (1 7) then do;n+1;h.add();end;
end;
n=ceil(h.num_items*rand('uniform'));
h.find();
format date ddmmyy10.;
drop n ;
run;
```

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Posted in reply to Ksharp

3 weeks ago

@Ksharp

Thank you very much for your help. But it seems that your code select dates randomly with no replacement. Could you show me how to choose random dates with replacement?

I am truly appreciate your support

Thank you very much for your help. But it seems that your code select dates randomly with no replacement. Could you show me how to choose random dates with replacement?

I am truly appreciate your support

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Posted in reply to trungcva112

3 weeks ago

I don't understand what you mean. My code indeed did replace sample.

`n=ceil(h.num_items*rand('uniform'));`

this code randomly pick up a date from the valid weekday .

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Posted in reply to trungcva112

3 weeks ago - last edited 3 weeks ago

Or here a combination of what @Astounding and @Ksharp posted:

```
data have;
infile cards expandtabs;
input Group $ Begdate : ddmmyy10. enddate : ddmmyy10.;
format Begdate enddate ddmmyy10.;
cards;
A 12-03-2005 25-08-2008
B 03-06-2001 10-09-2003
C 05-02-2011 21-06-2013
;
run;
data want(drop=_:);
set have;
format ran_date ddmmyy10.;
do _i=1 to 1000;
ran_date=Begdate + floor(rand('uniform')*(enddate-Begdate+1));
if weekday(ran_date) not in (1,7) then leave;
else call missing(ran_date);
end;
run;
```

N.B: The code above includes random selection of a date which is exactly the begin or end date (=borders included).

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Posted in reply to Patrick

3 weeks ago

Patrick,

That is not rigorously random sample yet .