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59 lines
1.8 KiB
SAS
59 lines
1.8 KiB
SAS
/**
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@file
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@brief Generates an md5 expression for hashing a set of variables
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@details This is the same algorithm used to hash records in
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[Data Controller for SAS](https://datacontroller.io) (free for up
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to 5 users).
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It is not designed to be efficient - it is designed to be effective,
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given the range of edge cases (large floating points, special missing
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numerics, thousands of columns, very wide columns).
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It can be used only in data step, eg as follows:
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data _null_;
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set sashelp.class;
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hashvar=%mp_md5(cvars=name sex, nvars=age height weight);
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put hashvar=;
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run;
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Unfortunately it will not run in SQL - it fails with the following message:
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> The width value for HEX is out of bounds. It should be between 1 and 16
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The macro will also cause errors if the data contains (non-special) missings
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and the (undocumented) `options dsoptions=nonote2err;` is in effect.
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This can be avoided in two ways:
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@li Global option: `options dsoptions=nonote2err;`
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@li Data step option: `data YOURLIB.YOURDATASET /nonote2err;`
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@param cvars= Space seperated list of character variables
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@param nvars= Space seperated list of numeric variables
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<h4> Related Programs </h4>
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@li mp_init.sas
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@version 9.2
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@author Allan Bowe
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**/
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%macro mp_md5(cvars=,nvars=);
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%local i var sep;
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put(md5(
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%do i=1 %to %sysfunc(countw(&cvars));
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%let var=%scan(&cvars,&i,%str( ));
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&sep put(md5(trim(&var)),$hex32.)
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%let sep=!!;
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%end;
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%do i=1 %to %sysfunc(countw(&nvars));
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%let var=%scan(&nvars,&i,%str( ));
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/* multiply by 1 to strip precision errors (eg 0 != 0) */
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/* but ONLY if not missing, else will lose any special missing values */
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&sep put(md5(trim(put(ifn(missing(&var),&var,&var*1),binary64.))),$hex32.)
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%let sep=!!;
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%end;
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),$hex32.)
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%mend mp_md5;
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