AttributeTrimmer
Removes specified leading and trailing characters from selected attributes.
Typical Uses
- Cleaning attribute data
- 删除一点点e space (non-printing characters) from attribute values
How does it work?
The AttributeTrimmer removes specific characters from the beginning and/or end of chosen attribute values.
It does not match specific character patterns, rather, as long as the next character is included in the list ofTrim Characters, it will continue to remove them until it encounters a character that is not in the list.
For example, suppose the attribute to trim had the value "This is a test" andTrim Typewas set toBoth(trimming from both the beginning and end of the value).
- IfTrim Charactershad the value "hit", the result would be "This is a tes".
- IfTrim Charactershad the value "HhIiTt", the result would be "s is a tes".
Trim Charactersmay be alphanumeric, and can include control characters. IfTrim Charactersis left blank (unspecified), “white space” will be removed - non-printing characters such as spaces, tabs, newlines, and carriage returns.
The attributes are output with any matching characters trimmed. Attributes that do not have matchingTrim Charactersare output untouched.
In this example, we start with a CSV file containing animal names and counts. Some animal names have varying numbers of extra spaces that need to be removed.
All features from the CSV file are routed into an AttributeTrimmer.
In the Parameters dialog, we select the attributeAnimalfor trimming, chooseTrim TypeBothto trim both the left and right-hand sides of the values, and leave theTrim Charactersfield blank - indicating we want white space removal.
The resulting output has clean Animal values, with spaces removed.
In this example, we start with a list of codes. They are all prefixed with the string “UID-”, and we wish to remove that prefix from the values.
The features are routed into an AttributeTrimmer with the intention of removing the prefix.
In the Parameters dialog, we selectTrim Typeas左(the location of the prefix), and enter the prefix stringUID-as theTrim Characters.
In the output file, the prefixes have been removed - but unfortunately, some additional characters have been trimmed as well. Because the AttributeTrimmer is not looking for a specific pattern of characters, if the first character(s) to the right of the prefix match any characters in theTrim Charactersstring, they will be removed as well.
As highlighted in the CorrectResults list, some of the initial characters beyond the prefix matched theTrim Characters.
A better choice to perform this task would be theStringReplacer, which will look for the exact pattern of the prefix.
Usage Notes
- To trim a specific prefix or suffix, or match any consistent string pattern, consider using theStringReplacer.
配置
Input Ports
Features with attributes you wish to trim.
Output Ports
Features with the selected attribute(s) trimmed according to your parameter selections, and all other attributes unmodified.
Parameters
Attributes to Trim | Select the attribute(s) to be trimmed. | ||||||||||||||
Trim Type | Characters may be trimmed from the right, left, or from both sides. | ||||||||||||||
Trim Characters | Enter individual characters to be trimmed. Characters will be trimmed from beginning, end, or both the beginning and the end, depending on the Trim Type selection. The trimmed characters are case sensitive. If you do not specify a trim character, white space is removed (spaces, tabs, newlines, and carriage returns).
Using Special/Control Characters
Characters can be expressed as regular characters but they can also include any number of control characters. Special character sequences are interpreted as shown below:
Defining Special CharactersYou can define special characters through the Text Editors. Click Open Text Editor from the parameter menu: Text Editor Enter characters using the shortcuts from the table above. Note:To see tab characters, click the Options menu on the bottom left and selectShow Spaces/Tabs. Note:This parameter is not a text string that is matched and removed. To remove an entire text string, use theStringReplacer. |
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Allow Trim Down to Nothing | If a given attribute value contains onlyTrim Characters, the character that remains depends on theTrim Type: forBothit will be the middle character, for左it will be the last character, and forRightit will be the first character. If theAllow Trim Down to Nothingoption is set toNo, the output of the trimming will have at least one character remaining. |
Editing Transformer Parameters
Using a set of menu options, transformer parameters can be assigned by referencing other elements in the workspace. More advanced functions, such as an advanced editor and an arithmetic editor, are also available in some transformers. To access a menu of these options, clickbeside the applicable parameter. For more information, see变压器Parameter Menu Options.
Defining Values
There are several ways to define a value for use in a Transformer. The simplest is to simply type in a value or string, which can include functions of various types such as attribute references, math and string functions, and workspace parameters. There are a number of tools and shortcuts that can assist in constructing values, generally available from the drop-down context menu adjacent to the value field.
Using the Text Editor
The Text Editor provides a convenient way to construct text strings (including regular expressions) from various data sources, such as attributes, parameters, and constants, where the result is used directly inside a parameter.
Using the Arithmetic Editor
The Arithmetic Editor provides a convenient way to construct math expressions from various data sources, such as attributes, parameters, and feature functions, where the result is used directly inside a parameter.
Conditional Values
Set values depending on one or more test conditions that either pass or fail.
Parameter Condition Definition Dialog
Content
Expressions and strings can include a number of functions, characters, parameters, and more.
When setting values - whether entered directly in a parameter or constructed using one of the editors - strings and expressions containing String, Math, Date/Time or FME Feature Functions will have those functions evaluated. Therefore, the names of these functions (in the form @<function_name>) should not be used as literal string values.
These functions manipulate and format strings. | |
Special Characters |
A set of control characters is available in the Text Editor. |
Math functions are available in both editors. | |
Date/Time Functions | Date and time functions are available in the Text Editor. |
These operators are available in the Arithmetic Editor. | |
These return primarily feature-specific values. | |
FME and workspace-specific parameters may be used. | |
Creating and Modifying User Parameters | 创建自己的可编辑的参数。 |
Reference
Processing Behavior |
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Feature Holding |
No |
Dependencies | |
FME Licensing Level | FME Base Edition and above |
Aliases | StringTrimmer |
History | |
Categories |
FME Community
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Examples may contain information licensed under the Open Government Licence – Vancouver