SAS信用卡评分之变量分段

这一篇的文章来讲变量分段，在我之前的文章中，涉及到变量分段的代码是有的，早开始的等高等宽分啊，后面的基于基尼系数以及基于iv值对于字符变量的分类都有。链接在这,这！这！这！。

sas字符变量基于iv值的最优分类

sas字符变量基于基尼系数的最优分类

sas分类变量（3）之排序后按人数分组

sas分类变量（2）之等宽分组

sas分类变量（1）之按分位数分组

但是我要是没记错的话，我好像还欠你们一个数值变量的最优分段。这篇文章如果后面还可以贴的话，那就附上数据集批量输出数值变量最优分段的代码。为什么说“可以贴的话”，那是我之前写过一篇文章，微信提醒我超过20000字啦，叫我删掉。

进入正题。当评分卡建模的时候用的逻辑回归，最好是将连续变量变成分段变量，即字符变量。把字符变量，观测的种类达到10种以上的时候，建议分下类，最好每个变量（无论数值还是字符）控制在3-7段之间，这是我的建议哈，要是你领导叫你分8段，你就千万就要听领导的。

然后，我来说下，我这里的最优分段怎么就是最优的呢?

01字符变量

先发这张图给粘上来，然后我就用简单粗暴的语言解释最优是怎么最优的。就是先把每种情况都列出来，刚开始每一种情况都是一类，然后你还要输入因变量，所以1中就是找出最优的二元分割方法，把原来的一大群先分两大类，然后第2的套路还是跟1一样的，知道分成5份。你问我二元分割最好的指标是什么，你还记得我之前写的代码之前都有带“基尼系数”，“iv值”吗，就是按照这个指标去分的啦。然后这里还要说一点就是，你要是一个变量，总共就1、2、3、4种情况，然后还要最优分段分五份这不是为难嘛。假设你觉得4种情况的分层没有特点，想分的有特点一点，那就可以试着分成3份，2份。分出来的结果对比一下iv值，要是3份的iv值比4份还高或者一样的话，那就是3份还要好些，因为我们都知道变量分段越多iv值越高。

02

数值变量

这是数值变量最优分段的图，其实套路跟字符变量很像，但是数值变量就多了顺序，所以还是有点跟字符有点不像。首先连续变量被分为大量等距的小分段，譬如区间是100的变量，然后就分成50段，那么就是1-2就是一组。那按照跟刚才的字符变量一样的分法类似，就是先分两份，只是对于字符变量多了顺序。但是这里这里要注意一点就是，你本来1、2、3代表的是类的话，在这里就需要把他转成字符，就不要是数值丢进去分段。同样的，要是你不知道分几段的时候，试几次，看下iv值，取一个你觉得最好的iv值。

我是分割线

好的，两种变量的分类也就这样了啦，好像也没写多少字哦，那就贴代码吧。

options mlogic;

options nomlogic;

%macro gvalue(binds,m_value);

proc sql noprint;

%local i j R N;/*生成局部变量*/

select max(bin)into:R from &binds;/**/

select sum(total) into: N from &binds;/**/

%do i=1 %to &R;

%local N_&i._1 N_&i._2 N_&i._s N_s_1 N_s_2;

Select sum(Ni1) into :N_&i._1 from &BinDS where Bin =&i ;

Select sum(Ni2) into :N_&i._2 from &BinDS where Bin =&i ;

Select sum(Total) into :N_&i._s from &BinDS where Bin =&i ;

Select sum(Ni1) into :N_s_1 from &BinDS ;

Select sum(Ni2) into :N_s_2 from &BinDS ;

%end;

quit;

/* 检查缺失值 */

%do i=1 %to &R;

%do j=1 %to 2;

%local N_&i._&j;

%if (&&N_&i._&j=.) or (&&N_&i._&j=0) %then %do ;

%let &M_Value=.;

%return;

%end;

%end;

%end;

%do i=1 %to &r;

%local E_&i;

%let E_&i=0;

%do j=1 %to 2;

%let E_&i = %sysevalf(&&E_&i - (&&N_&i._&j/&&N_&i._s)*%sysfunc(log(%sysevalf(&&N_&i._&j/&&N_&i._s))) );

%end;

%let E_&i = %sysevalf(&&E_&i/%sysfunc(log(2)));

%end;

%local E;

%let E=0;

%do j=1 %to 2;

%let E=%sysevalf(&E - (&&N_s_&j/&N)*%sysfunc(log(&&N_s_&j/&N)) );

%end;

%let E=%sysevalf(&E / %sysfunc(log(2)));

%local Er;

%let Er=0;

%do i=1 %to &r;

%let Er=%sysevalf(&Er+ &&N_&i._s * &&E_&i / &N);

%end;

%let &M_Value=%sysevalf(1 - &Er/&E);

%return;

%mend;

%macro CalcMerit(BinDS, ix, M_Value);

%local n_11 n_12 n_21 n_22 n_1s n_2s n_s1 n_s2;

proc sql noprint;

select sum(Ni1) into :n_11 from &BinDS where i<=&ix;

select sum(Ni1) into :n_21 from &BinDS where i> &ix;

select sum(Ni2) into : n_12 from &BinDS where i<=&ix ;

select sum(Ni2) into : n_22 from &binDS where i> &ix ;

select sum(total) into :n_1s from &BinDS where i<=&ix ;

select sum(total) into :n_2s from &BinDS where i> &ix ;

select sum(Ni1) into :n_s1 from &BinDS;

select sum(Ni2) into :n_s2 from &BinDS;

quit;

%local N E1 E2 E Er;

%let N=%eval(&n_1s+&n_2s);

%let E1=%sysevalf(-( (&n_11/&n_1s)*%sysfunc(log(%sysevalf(&n_11/&n_1s))) +

(&n_12/&n_1s)*%sysfunc(log(%sysevalf(&n_12/&n_1s)))) / %sysfunc(log(2)) ) ;

%let E2=%sysevalf(-( (&n_21/&n_2s)*%sysfunc(log(%sysevalf(&n_21/&n_2s))) +

(&n_22/&n_2s)*%sysfunc(log(%sysevalf(&n_22/&n_2s)))) / %sysfunc(log(2)) ) ;

%let E =%sysevalf(-( (&n_s1/&n  )*%sysfunc(log(%sysevalf(&n_s1/&n   ))) +

(&n_s2/&n  )*%sysfunc(log(%sysevalf(&n_s2/&n   )))) / %sysfunc(log(2)) ) ;

%let Er=%sysevalf(1-(&n_1s*&E1+&n_2s*&E2)/(&N*&E));

%let &M_value=&Er;

%return;

%mend;

%macro BestSplit(BinDs, BinNo);

%local mb i value BestValue BestI;

proc sql noprint;

select count(*) into: mb from &BinDs where Bin=&BinNo;

quit;

%let BestValue=0;

%let BestI=1;

%do i=1 %to %eval(&mb-1);

%let value=;

%CalcMerit(&BinDS, &i, Value);

%if %sysevalf(&BestValue<&value) %then %do;

%let BestValue=&Value;

%let BestI=&i;

%end;

%end;

data &BinDS;

set &BinDS;

if i<=&BestI then Split=1;

else Split=0;

drop i;

run;

proc sort data=&BinDS;

by Split;

run;

data &BinDS;

retain i 0;

set &BinDs;

by Split;

if first.split then i=1;

else i=i+1;

run;

%mend;

%macro CandSplits(BinDS, NewBins);

proc sort data=&BinDS;

by Bin PDV1;

run;

%local Bmax i value;

proc sql noprint;

select max(bin) into: Bmax from &BinDS;

%do i=1 %to &Bmax;

%local m&i;

create table Temp_BinC&i as select * from &BinDS where Bin=&i;

select count(*) into:m&i from Temp_BinC&i;

%end;

create table temp_allVals (BinToSplit num, DatasetName char(80), Value num);

run;quit;

%do i=1 %to &Bmax;

%if (&&m&i>1) %then %do; 

%BestSplit(Temp_BinC&i, &i);

data temp_trysplit&i;

set temp_binC&i;

if split=1 then Bin=%eval(&Bmax+1);

run;

Data temp_main&i;

set &BinDS;

if Bin=&i then delete;

run;

Data Temp_main&i;

set temp_main&i temp_trysplit&i;

run;

%let value=;

%GValue(temp_main&i,  Value);

proc sql noprint;

insert into temp_AllVals values(&i, "temp_main&i", &Value);

run;quit;

%end;

%end;

proc sort data=temp_allVals;

by descending value;

run;

data _null_;

set temp_AllVals(obs=1);

call symput("bin", compress(BinToSplit));

run;

Data &NewBins;

set Temp_main&Bin;

drop split;

run;

/* Clean the workspace */

/*proc datasets nodetails nolist library=work;*/

/* delete temp_AllVals %do i=1 %to &Bmax; Temp_BinC&i  temp_TrySplit&i temp_Main&i %end; ; */

/*run;*/

/*quit;*/

%mend;

%macro BinContVar(DSin, IVVar, DVVar, MMax, Acc, DSVarMap);

%local VarMax VarMin;

proc sql noprint;

select min(&IVVar), max(&IVVar) into :VarMin, :VarMax from &DSin;

quit;

%local Mbins i MinBinSize;

%let Mbins=%sysfunc(int(%sysevalf(1.0/&Acc)));

%let MinBinSize=%sysevalf((&VarMax-&VarMin)/&Mbins);

%do i=1 %to %eval(&Mbins);

%local Lower_&i Upper_&i;

%let Upper_&i = %sysevalf(&VarMin + &i * &MinBinSize);

%let Lower_&i = %sysevalf(&VarMin + (&i-1)*&MinBinSize);

%end;

%let Lower_1 = %sysevalf(&VarMin-0.0001);

%let Upper_&Mbins=%sysevalf(&VarMax+0.0001);

data Temp_DS;

set &DSin;

%do i=1 %to %eval(&Mbins-1);

if &IVVar>=&&Lower_&i and &IVVar < &&Upper_&i Then Bin=&i;

%end;

if &IVVar>=&&Lower_&Mbins and &IVVar <= &&Upper_&MBins Then Bin=&MBins;

keep &IVVar &DVVar Bin;

run;

data temp_blimits;

%do i=1 %to %Eval(&Mbins-1);

Bin_LowerLimit=&&Lower_&i;

Bin_UpperLimit=&&Upper_&i;

Bin=&i;

output;

%end;

Bin_LowerLimit=&&Lower_&Mbins;

Bin_UpperLimit=&&Upper_&Mbins;

Bin=&Mbins;

output;

run;

proc sort data=temp_blimits;

by Bin;

run;

proc freq data=Temp_DS noprint;

table Bin*&DVvar /out=Temp_cross;

table Bin /out=Temp_binTot;

run;

proc sort data=temp_cross;

by Bin;

run;

proc sort data= temp_BinTot;

by Bin;

run;

data temp_cont;

merge Temp_cross(rename=count=Ni2 ) temp_BinTot(rename=Count=total) temp_BLimits ;

by Bin;

Ni1=total-Ni2;

PDV1=bin;

label  Ni2= total=;

if Ni1=0 then output;

else if &DVVar=1 then output;

drop percent &DVVar;

run;

data temp_contold;

set temp_cont;

run;

proc sql noprint;

%local mx;

%do i=1 %to &Mbins;

select count(*) into : mx from Temp_cont where Bin=&i;

%if (&mx>0) %then %do;

select Ni1, Ni2, total, bin_lowerlimit, bin_upperlimit into  :Ni1,:Ni2,:total, :bin_lower, :bin_upper

from temp_cont where Bin=&i;

%if (&i=&Mbins) %then %do;

select max(bin) into :i1 from temp_cont where Bin<&Mbins;

%end;

%else %do;

select min(bin) into :i1 from temp_cont where Bin>&i;

%end;

%if (&Ni1=0) or (&Ni2=0) or (&total=0) %then %do;

update temp_cont set Ni1=Ni1+&Ni1 ,

Ni2=Ni2+&Ni2 ,

total=total+&Total

where bin=&i1;

%if (&i<&Mbins) %then %do;

update temp_cont set Bin_lowerlimit = &Bin_lower

where bin=&i1;

%end;

%else %do;

update temp_cont set Bin_upperlimit = &Bin_upper

where bin=&i1;

%end;

delete from temp_cont where bin=&i;

%end;

%end;

%end;

quit;

proc sort data=temp_cont;

by pdv1;

run;

%local m;

data temp_cont;

set temp_cont;

i=_N_;

Var=bin;

Bin=1;

call symput("m", compress(_N_));

run;

%local Nbins ;

%let Nbins=1; 

%DO %WHILE (&Nbins <&MMax);

%CandSplits(temp_cont, Temp_Splits);

Data Temp_Cont;

set Temp_Splits;

run;

%let NBins=%eval(&NBins+1);

%end;

data temp_Map1 ;

set temp_cont(Rename=Var=OldBin);

drop Ni2 PDV1 Ni1 i ;

run;

proc sort data=temp_Map1;

by Bin OldBin ;

run;

data temp_Map2;

retain  LL 0 UL 0 BinTotal 0;

set temp_Map1;

by Bin OldBin;

Bintotal=BinTotal+Total;

if first.bin then do;

LL=Bin_LowerLimit;

BinTotal=Total;

End;

if last.bin then do;

UL=Bin_UpperLimit;

output;

end;

drop Bin_lowerLimit Bin_upperLimit Bin OldBin total;

run;

proc sort data=temp_map2;

by LL;

run;

data &DSVarMap;

set temp_map2;

Bin=_N_;

run;

/* Clean the workspace */

/*proc datasets nodetails library=work nolist;*/

/* delete temp_bintot temp_blimits temp_cont temp_contold temp_cross temp_ds temp_map1*/

/*    temp_map2 temp_splits;*/

/*run; quit;*/

%mend;

%macro ApplyMap2(DSin, VarX, NewVarX, DSVarMap, DSout);

%local m i;

proc sql noprint;

select count(Bin) into:m from &DSVarMap;

quit;

%do i=1 %to &m;

%local Upper_&i Lower_&i Bin_&i;

%end;

data _null_;

set &DSVarMap;

call symput ("Upper_"||left(_N_), UL);

call symput ("Lower_"||left(_N_), LL);

call symput ("Bin_"||left(_N_), Bin);

run;

Data &DSout;

set &DSin;

IF &VarX < &Upper_1 Then &NewVarX=&Bin_1;

%do i=2 %to %eval(&m-1);

if &VarX >= &&Lower_&i and &VarX < &&Upper_&i Then &NewVarX=&&Bin_&i;

%end;

if &VarX >= &&Lower_&i  Then &NewVarX=&&Bin_&i;

DROP &VarX.;

Run;

%mend;

%macro var_namelist(data=,coltype=,tarvar=,dsor=);

%let lib=%upcase(%scan(&data.,1,'.'));

%let dname=%upcase(%scan(&data.,2,'.'));

%global var_list var_num;

proc sql ;

create table &dsor. as

select name

from sashelp.VCOLUMN

where left(libname)="&lib." and left(memname)="&dname." and type="&coltype." and lowcase(name)^=lowcase("&tarvar.") and lowcase(name)^="appl_id";

quit;

%mend;

%macro pub_best(data=,tarvar=,MMax=,ACC=,DSout=);

proc datasets lib=work;

delete _all_;

run;

%var_namelist(data=&data.,coltype=num,tarvar=&tarvar.,dsor=aa);

data _null_;

set aa;

call symput (compress("var"||left(_n_)),compress(name));

call symput(compress("n"),compress(_n_));

run;

%do i=1 %to &n.;

%put &&Var&i.;

%BinContVar(DSin=&data., IVVar=&&Var&i., DVVar=&tarvar.,MMax=&MMax., ACC=&Acc., DSVarMap=AA_1);

%ApplyMap2(DSin=&data., VarX=&&Var&i., NewVarX=N_&&Var&i., DSVarMap=AA_1, DSout=&DSout.);

%END;

%MEND;

这代码有点长，你就直接复制到sas里面看吧。

data=填入原始的数据集

tarvar=因变量;

MMax=分几组;

Acc=刚才是分几组，譬如你是1-100，那么你设定的是0.01，那就是分成100组，建议acc设定在0.01-0.05之间;

DSout=输出数据集。

代码是我调试好的，可以直接用。