Bootstrapping SAS EG vs SAS Viya

[smackerz1988]

Hi,

I'm currently waiting to get access for sas viya but I have a test case scenario to compare between sas eg and sas viya and just want to verify the sas viya code. For bootstrapping in sas eg I have this code 

proc surveyselect data=data​

out=BootSamples noprint​

seed=25 ​

reps=2000   ​

method=urs​

samprate=1​

outhits;​

run;

Am I right that this would be the equivalent code in sas viya or am i missing something?

/* Start CAS session and load data into CAS */
cas mysess sessopts=(caslib='casuser');
libname mylib cas sessref=mysess;

/* Load example data */
proc casutil;
    load data=data casout="sample" replace;
run;

/* Perform bootstrap resampling using the sampling action set */
proc cas;
    action sampling.srs result=r /
        table={caslib='casuser', name='sample'}
        output={casout={caslib='casuser', name='BootSamples', replace=true}}
        samppct=100 /* Sampling rate of 100% for bootstrap */
        method='URS' /* Unrestricted random sampling with replacement */
        seed=25 /* Seed for reproducibility */
        reps=2000; /* Number of bootstrap replicates */
        selection={name='Freq', includeFreq=true}; /* Include frequency counts in the output */
quit;

/* Fetch and display some of the bootstrap samples (Optional) */
proc cas;
    table.fetch / table={caslib='casuser', name='BootSamples'} to=10;
quit;

/* End CAS session */
cas mysess terminate;

[sbxkoenk]

Hello,

Method='URS' in sampling.srs action is not an existing parameter. Where did you get that from?

See :

Home > Analytics > SAS Data Science > CAS Bootstrapping
https://communities.sas.com/t5/SAS-Data-Science/CAS-Bootstrapping/m-p/931229#M10828

Koen

[smackerz1988]

Thanks for the link @sbxkoenk .So if I understand correctly if I'm using sas viya 4 I should use method = SRS instead?

[smackerz1988]

@sbxkoenk is this code more appropriate? 

/* Perform bootstrap resampling using the sampling action set */
proc cas;
    action loadActionSet / actionSet='sampling';
quit;

proc cas;
    action sampling.srs result=r /
        table={caslib='casuser', name='sample'}
        output={casOut={caslib='casuser', name='BootSamples', replace=true}}
        samppct=100 /* Sampling rate of 100% for bootstrap */
        replace=True /* Sampling with replacement */
        seed=25 /* Seed for reproducibility */
        reps=2000; /* Number of bootstrap replicates */
        selection={name='Freq', includeFreq=true}; /* Include frequency counts in the output */
quit;

I am unable to test it on sas viya currently but would really appreciate if I can verify it is a more accurate reflection of sas viya 4 functionality so I can compare and contrast with sas 9.4

[sbxkoenk]

The code is NOT correct.

The below sampling.srs parameters do not exist:

        replace=True /* Sampling with replacement */
        reps=2000; /* Number of bootstrap replicates */

Here are a few links to get you started.

1. https://github.com/statmike/Resampling-Methods-in-SAS-Viya     : Fast, easy resampling methods using the SAS Viya CAS Engine (bootstrap, double-Bootstrap, jackknife)
2. Bootstrap Resampling At Scale: Part 1 (of 3) dd. 03 March 2020
   https://statmike.com/blog/sgf2020p1
3. Bootstrap Resampling At Scale: Part 2 (of 3) dd. 04 March 2020
   https://statmike.com/blog/sgf2020p2
4. Bootstrap Resampling At Scale: Part 3 (of 3) dd. 05 March 2020
   https://statmike.com/blog/sgf2020p3

Please learn about the APPLYROWORDER procedure-option (e.g. PROC PARTITION) and the ADDROWID data set option, as you will need these to ensure reproducibility.

Last but not least , PROC SURVEYSELECT runs on the compute server (SPRE) in SAS Viya 4 ... you can still use this SAS/STAT procedure (it's just not CAS-enabled).
You can turn to the CAS engine (distributed computing) for the remainder of your calculations.

Koen

[smackerz1988 · Accepted solution]

This is basically the code that I need. Thanks for your help 

/* Initialize CAS Session */
cas mysess sessopts=(caslib='casuser');
libname mylib cas sessref=mysess;

/* Load Dataset into CAS */
proc casutil;
    load data=sashelp.cars casout="sample" replace;
quit;

/* Load and Define Action Set */
proc cas;
    builtins.actionSetFromTable / table={caslib="Public" name="resampleActionSet.sashdat"} name="resample";
quit;

/* Bootstrap in CAS with Timing */
%let _time1=%sysfunc(time());

proc cas;
    resample.bootstrap / 
        intable='sample' 
        B=200 
        seed=12345 
        Bpct=1 
        case='ID' 
        strata='none' 
        strata_table='none';
    datastep.runcode result=t / code='data sample_bs; set sample_bs; host=_hostname_; threadid=_threadid_; run;';
    simple.crossTab / table={name="sample_bs" where="bag=1"} row="bsid" col="host" aggregator="N";
    simple.crossTab / table={name="sample_bs" where="bag=1"} row="bsid" col="threadid" aggregator="N";
run;

%let _time2=%sysfunc(time());
%let elapsed = %sysevalf(&_time2 - &_time1);
%let minutes = %sysfunc(floor(%sysevalf(&elapsed/60)));
%let seconds = %sysevalf(&elapsed - (&minutes*60));
%put CAS Bootstrap Time: &minutes minutes &seconds seconds;

/* Clear CAS Session */
*cas mysess clear; 

[sbxkoenk]

Indeed.

Just a reminder ... so you (and others) are aware.

resample.bootstrap is not a SAS-supplied action. It's a custom action programmed by the owner of the GitHub - repository.

So, you also need the code to define the action in your SAS Viya environment.

BR, Koen

[smackerz1988]

@sbxkoenk Just to clarify the resampleActionSet action was already available in the public cas library file without having to download or clone directly from the github repository?. Is that correct?. I guess what I need to understand how is sas viya able to use the .sashdat file to load from github repository? Hope I'm making sense. I know when I run this code 

/* Load and Define Action Set */
proc cas;
    builtins.actionSetFromTable / table={caslib="Public" name="resampleActionSet.sashdat"} name="resample";
quit;

/* List Available Action Sets */
proc cas;
    action builtins.actionSetInfo;
run;

I am able to see resample and that it is user defined 

[sbxkoenk]

---

@smackerz1988 wrote:

@sbxkoenk Just to clarify the resampleActionSet action was already available in the public cas library file without having to download or clone directly from the github repository?. Is that correct?.

---

Not correct.

You have to make the custom action set -- that you defined -- available in the PUBLIC CAS library (as a *.sashdat file) and then load from there.

(No need to clone repository ... just download the *.sas program and run or copy/paste and run)

Here's how to proceed (see also the README of the GitHub repository):

Setting up the actions in your environment

Run the code in resample - defineActionSet.sas. Some lines that may need changing:

• line 1: connects to a CAS session
• To Save the actions for future sessions and use by other users:
  • line 174: create an in-memory table of the action set
  • line 175: persist the in-memory table in .sashdat file. Here it is pointed as caslib="Public".
• If you need to remove the action set then uncomment and use:
  • line 177: removes the persisted in-memory table

Actions Instructions

To use the actions you will need to load the user defined actions with:

builtins.actionSetFromTable / table={caslib="Public" name="resampleActionSet.sashdat"} name="resample";

BR,
Koen

[smackerz1988]

Ah I understand now! Thanks for clarifying that makes sense!