User's Manual

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Chapter 6
Figure 6-1
Specifying missing values for a continuous variable
Reading in mixed data. Note that when you are re ading in fields with numeric storag e (either
integer, real, time, timest amp, or date), any non-numeric values are set to null or system missing.
This is because, unlike some applications, does not allow mixed storage types within a field. To
avoid this, any fields with mix ed data should be read in as strings by changing the storage type in
the source node or exter nal application as necessa r y.
Reading empty strings from Oracle. When reading from or writing to an Oracle database, be aw are
that, unlike SPSS Modeler and unlike most othe r databases, Or acle treats and store s empty string
values as equivalent to null values. This means that the s ame data extracted from an Oracle
database may behave differently than when extracted from a file or another database, and the data
may return different results .
Handling Missing Values
You should decide how to treat missing values in li ght of your business or domain knowledge. To
ease training time and increase accuracy, you may w an t to remove blanks from your d ata set. On
the ot
her hand, the pres ence of blan k values may lea d to new business opp ortuniti es or a dditional
insights. In choosing the best technique, you should consider the following aspects of your data:
 Size of the data set
 Number of fields containing blanks
 Amount of missing inf ormation