# Logistic model - numerical vs. categorical covariates & target

#### syswizard

##### New Member
I am using a powerful analytics tool built by Oracle (Data Miner). I am trying to determine the probability of death for a patient given the presence of certain diagnosis codes. There will be up to 40 possible codes as column references (covariates) in the model.
Any reason why I must convert the presence indicator to a numeric 0/1 design variable ? Same thing with the target variable (death) - must it be 0/1 (0=alive, 1=death) ?

I noticed that SAS users do this regularly, but my modelling package allows for categorical "Y","N" instead.

#### Englund

##### TS Contributor
If your software allows string instead of numeric coding I do not see any reason to recode the DV-

#### noetsi

##### Fortran must die
I am not sure I understand what you are asking, but if you have a choice between coding the DV as a percentage (and thus quantiative) variable or 1/0 I would chose the former. With the former you can use (assuming other assumptions are met) linear regression which has a number of advantages over doing logistic regression (what you have to do with 1/0 coding).

#### syswizard

##### New Member
I am not sure I understand what you are asking, but if you have a choice between coding the DV as a percentage (and thus quantiative) variable or 1/0 I would chose the former. With the former you can use (assuming other assumptions are met) linear regression which has a number of advantages over doing logistic regression (what you have to do with 1/0 coding).
In my case, it's just logistic - True / False for both target variable and dependent covariates.
But that makes sense....and could be the reason for using the 1/0....so that linear regression would be a possibility.

#### syswizard

##### New Member
If your software allows string instead of numeric coding I do not see any reason to recode the DV-
My only thought was : "Is 0/1 more efficient ?" But I have a funny feeling the "Y","N" gets converted to 1/0 internally within the Data Miner.

#### Englund

##### TS Contributor
But I have a funny feeling the "Y","N" gets converted to 1/0 internally within the Data Miner.
That is probably the case.