# Special fields #

Special functions are used to denote the specific fields under examination, or to generate a list of fields as input\.

For example, when deriving multiple fields at once, you should use `@FIELD` to denote perform this derive action on the selected fields\. Using the expression `log(@FIELD)` derives a new log field for each selected field\.

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CLEM special fields  

Table 1\. CLEM special fields

| Function                      | Result | Description                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
| ----------------------------- | ------ | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
| `@FIELD`                      | *Any*  | Performs an action on all fields specified in the expression context\.                                                                                                                                                                                                                                                                                                                                                                                                   |
| `@TARGET`                     | *Any*  | When a CLEM expression is used in a user\-defined analysis function, `@TARGET` represents the target field or "correct value" for the target/predicted pair being analyzed\. This function is commonly used in an Analysis node\.                                                                                                                                                                                                                                        |
| `@PREDICTED`                  | *Any*  | When a CLEM expression is used in a user\-defined analysis function, `@PREDICTED` represents the predicted value for the target/predicted pair being analyzed\. This function is commonly used in an Analysis node\.                                                                                                                                                                                                                                                     |
| `@PARTITION_FIELD`            | *Any*  | Substitutes the name of the current partition field\.                                                                                                                                                                                                                                                                                                                                                                                                                    |
| `@TRAINING_PARTITION`         | *Any*  | Returns the value of the current training partition\. For example, to select training records using a Select node, use the CLEM expression: `@PARTITION_FIELD = @TRAINING_PARTITION` This ensures that the Select node will always work regardless of which values are used to represent each partition in the data\.                                                                                                                                                    |
| `@TESTING_PARTITION`          | *Any*  | Returns the value of the current testing partition\.                                                                                                                                                                                                                                                                                                                                                                                                                     |
| `@VALIDATION_PARTITION`       | *Any*  | Returns the value of the current validation partition\.                                                                                                                                                                                                                                                                                                                                                                                                                  |
| `@FIELDS_BETWEEN(start, end)` | *Any*  | Returns the list of field names between the specified start and end fields (inclusive) based on the natural (that is, insert) order of the fields in the data\.                                                                                                                                                                                                                                                                                                          |
| `@FIELDS_MATCHING(pattern)`   | *Any*  | Returns a list a field names matching a specified pattern\. A question mark (`?`) can be included in the pattern to match exactly one character; an asterisk (`*`) matches zero or more characters\. To match a literal question mark or asterisk (rather than using these as wildcards), a backslash (`\`) can be used as an escape character\.<br><br>Note: This requires a string literal as an argument; it can't use a nested expression to generate the argument\. |
| `@MULTI_RESPONSE_SET`         | *Any*  | Returns the list of fields in the named multiple response set\.                                                                                                                                                                                                                                                                                                                                                                                                          |

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