topic Re: Why is PROC MI ---FCS Logistic failing in SAS 9.4 to generate impute on categorical fields? in Statistical Procedures

Why is PROC MI ---FCS Logistic failing in SAS 9.4 to generate impute on categorical fields?

CloudcroftS_NWU — Sat, 13 Feb 2016 10:04:07 GMT

Hi,

I am confused why I am having to translate 3 of my 4 categorical variables with missing values that were cast as $Char4. into numerical variables in order for the PROC MI statement with FCS to work. I thought the whole point of PROC MI > FCS > LOGISTIC was to impute when the data is categorical. In fact, I've used it in the past to impute a "Job" field on an insurance dataset that was missing values so I know it works --though that was cast as a Text13. field. Does that matter????

I don't get why the PROC MI is failing for the Memory_Technology field which is a $char18. categorical field.

Also, if I use the LOGISTIC model which I thought I was reading was for categorical variables it returns non-categorical variables (eg. 1022.7814 when 1000 is a possibility or the next nearest category 1024).

Please see the attached data file and the code I am using.

I got the right results using this for 3 of the 4 fields (categories were appropriately generated but not for Memory_Technology):

PROC MI DATA=mydata1.comp2 seed=123 nimpute=15 OUT=impRSLTS;
       CLASS Memory_Technology Max_Horizontal_Resolution Installed_Memory
              Processor_Speed Processor Manufacturer Operating_System;
   FCS NBITER=5 DISCRIM(Memory_Technology Max_Horizontal_Resolution Installed_Memory Processor_Speed/details); * Use 5 burn-in iterations;
   VAR Memory_Technology Max_Horizontal_Resolution Installed_Memory Processor_Speed
       Processor Manufacturer Warranty_days
       dv_Infrared dv_Bluetooth dv_DockStnPrtRep_yy dv_DockStnPrtRep_yn
       dv_DockStnPrtRep_ny dv_DockStnPrtRep_nn dv_Fingerprint dv_Subwoofer
       SQRTprice dv_CDMA Operating_System dv_Ext_Battery;
RUN;

It's showing the patterns for impute with 'X' never missing for Memory_Technology but it is missing in 63 cases.

*UGH!*

Re: Why is PROC MI ---FCS Logistic failing in SAS 9.4 to generate impute on categorical fields?

StatsGeek — Mon, 15 Feb 2016 15:12:30 GMT

Hi,

The problem lies with the data. Run the following syntax:

proc freq data = laptops_dataset_raw;
tables Memory_Technology;
run;

It shows that MEMORY_TECHNOLOGY has no missing values, but it does have values are coded as '?'. A question mark is not recognized as a missing value in SAS. Recode the question marks to SAS missing values. Note that this should also be done for other variables that use question marks (e.g., MAX_HORIZONTAL_RESOLUTION). After the data are cleaned up, try running PROC MI again.

Best,

Steve

Re: Why is PROC MI ---FCS Logistic failing in SAS 9.4 to generate impute on categorical fields?

CloudcroftS_NWU — Thu, 18 Feb 2016 00:39:12 GMT

Yes...that was done prior to running the PROC. That's how I got the three
values generated that were numerical. It is the categorical variable that
is failing. Even with and missing value replacing the question mark.

Re: Why is PROC MI ---FCS Logistic failing in SAS 9.4 to generate impute on categorical fields?

peeeeekaaaaa — Tue, 16 Feb 2016 08:03:10 GMT

Hi,
Well, although you tried to replace the question marks, you did not actually... There is a difference between numeric and categorical missing values in SAS. The '.' character is a valid character for character variables, not a missing value. You have several options, e.g. use IF(Memory_Technology='?') THEN Memory_Technology=''; or IF(Memory_Technology='?') THEN call missing(Memory_Technology); in the data step.

Note also that comparisons like IF(Processor_Speed='?') do not make much sense for numeric variables since, well, they are numeric and '?' is a character...

Please consider taking some of the free SAS tutorials found at http://support.sas.com/training/tutorial/ You should find the "Free SAS Programming 1 e-Course" particularly useful.

Best,
PK