| expr | Field calculator |
| -fout <field> | field for storing the result |
| -expr <expr>; | expression to be evaluated |
| [-dout <dataout>] | output data frame for field |
| [-v] | verbose evaluation |
This command works as a data record calculator. A given expression is evaluated in a loop for each data record. The result values are stored in a new field (inside a data frame, if it has been specified). More information about expressions can be found in section 4.2.1.
Example (ex4.3): This example shows some basic operations for fields and an error message.
NDA> load boston.dat
NDA> expr -dout boston -fout znprice
-expr 'boston.rate' / ('boston.zn'+0.0001);
NDA> expr -dout boston -fout lowCrim -expr 'boston.crim' < 3;
# Cannot divide by string
NDA> expr -dout boston -fout someVar -expr 'boston.dis' / "xxx";
Returned error -409: Operand type mismatch for operator