topic Re: Setting some values of a continuous variable to missing randomly in SAS Programming

Setting some values of a continuous variable to missing randomly

mmovahed — Wed, 06 Nov 2019 17:39:35 GMT

I like to replace some values of a continuous variable to missing by random. I wonder what is the code in SAS for this.

Also Like to know if I can do multiple imputation for variable with whole missing values based on other variables in the data set. If so I wonder what is SAS codes for this as well.

Thanks

Re: Setting some values of a continuous variable to missing randomly

PaigeMiller — Wed, 06 Nov 2019 17:45:02 GMT

@mmovahed wrote:

I like to replace some values of a continuous variable to missing by random. I wonder what is the code in SAS for this.

Seems like an odd thing to do.

data want;
    set have;
    random=rand('uniform');
    if random<0.2 then x=.;
run;

Also Like to know if I can do multiple imputation for variable with whole missing values based on other variables in the data set. If so I wonder what is SAS codes for this as well.

Look at the examples in the documentation for PROC MI.

Re: Setting some values of a continuous variable to missing randomly

mmovahed — Wed, 06 Nov 2019 18:18:32 GMT

Thanks. It was useful.

Re: Setting some values of a continuous variable to missing randomly

hashman — Wed, 06 Nov 2019 19:50:07 GMT

@mmovahed:

The answer depends on whether you want to replace a variable with a missing value:

in an exact number of observations
approximately in some percentage of observations

A program for #1 will be quite different (and more complex - there're different algorithms for doing it) than for #2 at which @PaigeMiller has hinted.

And also it depends on whether every time you run the code you want to:

get exactly the same results
get different results
pick the observations on run #n all different from run #m
the missing values to be distributed uniformly or in some other manner

and possibly a number of other factors.

Kind regards

Paul D.

Re: Setting some values of a continuous variable to missing randomly

ballardw — Wed, 06 Nov 2019 23:10:04 GMT

@mmovahed wrote:

Also Like to know if I can do multiple imputation for variable with whole missing values based on other variables in the data set. If so I wonder what is SAS codes for this as well.

You may need to describe exactly what you mean by "whole missing values ". That sort of sounds like you have no actual values for a variable. Without at least a few values it is going to be real hard to determine any sort of rule that uses other variables to impute.

If you have a categorical variable that should have 4 levels but one of the levels doesn't appear, for example, then what rule would be used to determine the missing should be the category with no representation?

Re: Setting some values of a continuous variable to missing randomly

mmovahed — Wed, 06 Nov 2019 23:33:19 GMT

Hi

Thanks for your explanation. You are right. I think we need at least few available values for the variable with missing.

M