The R language has four symbols that are used to represent special numerical values.
The symbol NA represents a missing value. 
                  
The symbol Inf represents positive infinity. 
                  
The symbol –Inf represents positive infinity. 
                  
The symbol NaN represents a “NaN,” which is a floating-point value that represents an undefined value such as the result of the division  .
. 
                  
The SAS language has 28 symbols that are used to represent special numerical values.
The symbol . represents a generic missing value. 
                  
The symbols .A–.Z and ._ are also missing values. Some applications use .I to represent positive infinity and use .M to represent negative infinity. 
                  
The following table shows how special numeric values in R are converted to SAS missing values:
| Value in R | SAS Missing Value | 
|---|---|
| Inf | .I | 
| –Inf | .M | 
| NA | . | 
| NaN | . | 
The following table shows how SAS missing values are converted when data are transferred to R:
| SAS Missing Value | Value in R | 
|---|---|
| .I | Inf | 
| .M | –Inf | 
| All others | NA |