I am writing a formula in SAS. I need to use the standard deviation and the percentiles in all of it. But I am not sure how to write that in SAS.
data test;
set test1;
if ((the 100th percentile of X)-(99th percentile of X))>(SD of X) then delete;
run;
I am just not sure how to write those out in SAS
The percentile and standard deviation are characteristics of the entire data, not just one observation. Your logic seems to suggest you would delete every observation. Presumably you actually want to compare each observation to some feature of the distribution.
The basic approach is to add the percentiles and standard deviation that you want as new variables to your data. You can use proc univariate with an output statement to calculate the statistics you're interested in and save them to a new data set.
You then merge this back into your original data, so you will now have the variables you need. At that point you can use essentially the same syntax you already have.
This should get you started:
data tmp;
do i=1 to 100;
x=rannor(123);
output;
end;
run;
proc univariate data=tmp noprint;
var x;
output out=pctls max=max p99=p99 std=std;
run;
data tmp;
if _n_=1 then do;
set pctls;
end;
set tmp;
/* Just making up a condition here */
if x>p99 then delete;
run;
Related
i have a data that contain 30 variable and 2000 Observations.
I want to calculate regression in a loop, whan in each step I delete the i row in the data.
so in the end I need thet my output will be 2001 regrsion, one for the regrsion on all the data end 2000 on each time thet I drop a row.
I am new to sas, and I tray to find how to do it withe macro, but I didn't understand.
Any comments and help will be appreciated!
This will create the data set I was talking about in my comment to Chris.
data del1V /view=del1v;
length group _obs_ 8;
set sashelp.class nobs=nobs;
_obs_ = _n_;
group=0;
output;
do group=1 to nobs;
if group eq _n_ then;
else output;
end;
run;
proc sort out=analysis;
by group;
run;
DATA NEW;
DATA OLD;
do i = 1 to 2001;
IF _N_ ^= i THEN group=i;
else group=.;
output;
end;
proc sort data=new;
by group;
proc reg syntax;
by group;
run;
This will create a data set that is much longer. You will only call proc reg once, but it will run 2001 models.
Examining 2001 regression outputs will be difficult just written as output. You will likely need to go read the PROC REG support documentation and look into the output options for whatever type of output you're interested in. SAS can create a data set with the GROUP column to differentiate the results.
I edited my original answer per #data null suggestion. I agree that the above is probably faster, though I'm not as confident that it would be 100x faster. I do not know enough about the costs of the overhead of proc reg versus the cost of the group by statement and a larger data set. Regardless the answer above is simpler programming. Here is my original answer/alternate approach.
You can do this within a macro program. It will have this general structure:
%macro regress;
%do i=1 %to 2001;
DATA NEW;
DATA OLD;
IF _N_=&I THEN DELETE;
RUN;
proc reg syntax;
run;
%end;
%mend;
%regress
Macros are an advanced programming function in SAS. The macro program is required in order to do a loop of proc reg. The %'s are indicative of macro functions. &i is a macro variable (& is the prefix of a macro variable that is being called). The macro is created in a block that starts and ends with %macro / %mend, and called by %regress.
Examining 2001 regression outputs will be difficult just written as output. You will likely need to go read the PROC REG support documentation and look into the output options for whatever type of output you're interested in. Use &i to create a different data set each time and then append together as part of the macro loop.
I have a data where I have various types of loan descriptions, there are at least 100 of them.
I have to categorise them into various buckets using if and then function. Please have a look at the data for reference
data des;
set desc;
if loan_desc in ('home_loan','auto_loan')then product_summary ='Loan';
if loan_desc in ('Multi') then product_summary='Multi options';
run;
For illustration I have shown it just for two loan description, but i have around 1000 of different loan_descr that I need to categorise into different buckets.
How can I categorise these loan descriptions in different buckets without writing the product summary and the loan_desc again and again in the code which is making it very lengthy and time consuming
Please help!
Another option for categorizing is using a format. This example uses a manual statement, but you can also create a format from a dataset if you have the to/from values in a dataset. As indicated by #Tom this allows you to change only the table and the code stays the same for future changes.
One note regarding your current code, you're using If/Then rather than If/ElseIf. You should use If/ElseIf because then it terminates as soon as one condition is met, rather than running through all options.
proc format;
value $ loan_fmt
'home_loan', 'auto_loan' = 'Loan'
'Multi' = 'Multi options';
run;
data want;
set have;
loan_desc = put(loan, $loan_fmt.);
run;
For a mapping exercise like this, the best technique is to use a mapping table. This is so the mappings can be changed without changing code, among other reasons.
A simple example is shown below:
/* create test data */
data desc (drop=x);
do x=1 to 3;
loan_desc='home_loan'; output;
loan_desc='auto_loan'; output;
loan_desc='Multi'; output;
loan_desc=''; output;
end;
data map;
loan_desc='home_loan'; product_summary ='Loan '; output;
loan_desc='auto_loan'; product_summary ='Loan'; output;
loan_desc='Multi'; product_summary='Multi options'; output;
run;
/* perform join */
proc sql;
create table des as
select a.*
,coalescec(b.product_summary,'UNMAPPED') as product_summary
from desc a
left join map b
on a.loan_desc=b.loan_desc;
There is no need to use the macro language for this task (I have updated the question tag accordingly).
Already good solutions have been proposed (I like #Reeza's proc format solution), but here's another route which also minimizes coding.
Generate sample data
data have;
loan_desc="home_loan"; output;
loan_desc="auto_loan"; output;
loan_desc="Multi"; output;
loan_desc=""; output;
run;
Using PROC SQL's case expression
This way doesn't allow, to my knowledge, having several criteria on a single when line, but it really simplifies coding since the resulting variable's name needs to be written down only once.
proc sql;
create table want as
select
loan_desc,
case loan_desc
when "home_loan" then "Loan"
when "auto_loan" then "Loan"
when "Multi" then "Multi options"
else "Unknown"
end as product_summary
from have;
quit;
Otherwise, using the following syntax is also possible, giving the same results:
proc sql;
create table want as
select
loan_desc,
case
when loan_desc in ("home_loan", "auto_loan") then "Loan"
when loan_desc = "Multi" then "Multi options"
else "Unknown"
end as product_summary
from have;
quit;
I have a variable of weight, wprm, that takes integer values. I would like to have one that is the weight "normalized", that is to say wprm/sum(wprm)
I can do that by outputing a proc summary ant then a merge to put it back with the original data, and then dividing my wprm variable, but it seems a bit heavy, is there a simpler way ?
Use PROC STDIZE or PROC STANDARD - they both allow various normalization methods.
proc stdize data=have method=sum out=want;
var wprm;
run;
You can grab the macro %simple_normalize from here.
data test;
do i=1 to 10;
output;
end;
run;
%simple_normalize(test,i);
The other common option is SQL, but it will post a warning/note to the log that many people don't like.
proc sql;
create table want as
select a.*, a.wprm/sum(a.wprm) as weight
from have;
quit;
I am currently running a macro code in SAS and I want to do a calculation with regards to max and min. Right now the line of code I have is :
hhincscaled = 100*(hhinc - min(hhinc) )/ (max(hhinc) - min(hhinc));
hhvaluescaled = 100*(hhvalue - min(hhvalue))/ (max(hhvalue) - min(hhvalue));
What I am trying to do is re-scale household income and value variables with the calculations below. I am trying to subtract the minimum value of each variable and subtract it from the respective maximum value and then scale it by multiplying it by 100. I'm not sure if this is the right way or if SAS is recognizing the code the way I want it.
I assume you are in a Data Step. A Data Step has an implicit loop over the records in the data set. You only have access to the record of the current loop (with some exceptions).
The "SAS" way to do this is the calculate the Min and Max values and then add them to your data set.
Proc sql noprint;
create table want as
select *,
min(hhinc) as min_hhinc,
max(hhinc) as max_hhinc,
min(hhvalue) as min_hhvalue,
max(hhvalue) as max_hhvalue
from have;
quit;
data want;
set want;
hhincscaled = 100*(hhinc - min_hhinc )/ (max_hhinc - min_hhinc);
hhvaluescaled = 100*(hhvalue - min_hhvalue)/ (max_hhvalue - min_hhvalue);
/*Delete this if you want to keep the min max*/
drop min_: max_:;
run;
Another SAS way of doing this is to create the max/min table with PROC MEANS (or PROC SUMMARY or your choice of alternatives) and merge it on. Doesn't require SQL knowledge to do, and probably about the same speed.
proc means data=have;
*use a class value if you have one;
var hhinc hhvalue;
output out=minmax min= max= /autoname;
run;
data want;
if _n_=1 then set minmax; *get the min/max values- they will be retained automatically and available on every row;
set have;
*do your calculations, using the new variables hhinc_max hhinc_min etc.;
run;
If you have a class statement - ie, a grouping like 'by state' or similar - add that in proc means and then do a merge instead of a second set in want, by your class variable. It would require a sorted (initial) dataset to merge.
You also have the option of doing this in SAS-IML, which works more similarly to how you are thinking above. IML is the SAS interactive matrix language, and more similar to r or matlab than the SAS base language.
In SAS, how can I assign a variable coming from either the OUTEST or OUTSTAT functions to be used in a loop?
For example, say I want to run some sort of iterative analysis until my mean (average) reaches a certain threshold. I know how to extract the mean using either OUTEST or OUTSTAT, but then how can I perform operations or blocks of code on it?
Thank you.
If you are interested in details, I am trying to perform backward selection of VIFs (to remove multicollinearity). Unfortunately, SAS doesn't seem to have a 'SELECTION=BACKWARD' feature for this...
EDIT: Updated with sample code:
%MACRO MULTICOLLINEARITY(TABLE_SUFFIX,YVAR,FIELDS,MAX_VIF);
/* PRELIMINARY PROC REG ON ALL FIELDS*/
PROC REG DATA=TABLE_&TABLE_SUFFIX. NOPRINT;
MODEL &YVAR = &FIELDS / VIF COLLIN NOINT;
ODS OUTPUT PARAMETERESTIMATES=PAREST1;
RUN;
/* RETAIN NON-NULL VIF FIELDS ONLY */
DATA NO_NULL_VIF;
SET PAREST1 (WHERE=(VarianceInflation <> .));
RUN;
/* CREATE VARIABLE LIST OF NON-NULL VIF FIELDS */
PROC SQL;
SELECT VARIABLE
INTO :NO_NULL_VIF_FIELDS SEPARATED BY ' '
FROM NO_NULL_VIF;
QUIT;
/* RE-RUN REGRESSION WITH NON-NULL VIF FIELDS ONLY */
PROC REG DATA=TABLE_&TABLE_SUFFIX. NOPRINT;
MODEL &YVAR = &NO_NULL_VIF_FIELDS / VIF COLLIN NOINT;
ODS OUTPUT PARAMETERESTIMATES=PAREST2;
RUN;
/* START ITERATION OF DROPPING THE HIGHEST VIF UNTIL THE CRITERIA IS MET */
???
%MEND;
%MULTICOLLINEARITY(, RESPONSE, &INPUT_FIELDS,???)
And by criteria I mean VIF_MAX < N where N is some threshold specified in the macro. For example, if we want to retain only fields with VIF less than 5, then it should drop the highest one, re-run the PROC REG, drop the highest, re-run, etc. etc. until the highest on is less than 5.
First off - I'd verify that you can't do this using PROC MODEL. I'm not a regression guy so I don't know for sure. Might be worth posting on a more stat-focused site; CV isn't really appropriate since they're not generally trying to answer software questions, but maybe communities.sas.com . I would find it surprising if this wasn't directly possible in PROC MODEL and/or in one of the more complicated procs.
Second, the way I'd approach this is to write a recursive macro. Take out the first part (the non-null VIF fields) and either move that to an outer macro that just runs once, or make it an expectation of the programmer to do on his/her own (unless this is not feasible, and/or can change with iterations - not something I'm knowledgeable of). Then do something like this:
%MACRO MULTICOLLINEARITY(TABLE_SUFFIX,YVAR,FIELDS,MAX_VIF);
ods _all_ close;
%put Running with &fields; *note which fields currently running;
*also may want to include a run # counter as parameter;
PROC REG DATA=TABLE_&TABLE_SUFFIX.;
MODEL &YVAR = &FIELDS / VIF COLLIN NOINT;
ODS OUTPUT PARAMETERESTIMATES=PAREST2;
RUN;
quit;
*Data step to analyse PAREST2 and see if any of the fields can be dropped;
proc sort data=parest2;
by descending varianceinflation;
run;
data _null_;
set parest2(obs=1);
if varianceinflation > &max_vif then do;
fields_run = tranwrd("&fields",trim(variable),' ');
if not missing(fields_run) then do;
call_string = cats('%multicollinearity(',"&table_suffix.,&yvar.,",fields_run,",&max_vif.)");
call execute(call_string);
end;
end;
else do;
put "Stopped with Max VIF:" variable "=" varianceinflation;
run;
ods preferences;
%MEND MULTICOLLINEARITY;
Then you call it once with the full field list, and it calls itself in the CALL EXECUTE if there is still a parameter left. An incremented # of runs may be helpful (both to see how many times it ran in your log, and to be able to make sure that you don't end up in an infinite loop if you make a mistake with the fields variable deletion.)
I would run this with OPTION NONOTES NOSOURCE; and none of the symbogen/mprint stuff on, so you can just get the %put/put statements in your log.