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- remove en_US postfix - remove translated files (translation were moved to ts files earlier) - remove unused jQuery (python help doesn't use it anymore) - change expression label in QgsQueryBuilder and add context help (partly fixes #8129)
60 lines
3.6 KiB
Plaintext
60 lines
3.6 KiB
Plaintext
<h3>Field Calculator</h3>
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The field calculator allows you to update fields with expressions.
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<h4>Supported Operations</h4>
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<table border=1>
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<tr>
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<th>Operation</th>
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<th>Description</th>
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</tr>
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<tr>
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<td>
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<tt>column_name</tt><br>
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<tt>"column_name"</tt>
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</td>
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<td>value of field <tt>column_name</tt></td>
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</tr>
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<tr><td>'<tt>string</tt>'</td><td>literal string value</td></tr>
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<tr><td><tt>number</tt></td><td>number</td></tr>
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<tr><td>NULL</td><td>null value</td></tr>
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<tr><td>exp(<tt>a</tt>)</td><td>Euler's number e to the power of <tt>a</tt></td></tr>
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<tr><td>ln(<tt>a</tt>)</td><td>natural log (i.e. base e) of <tt>a</tt></td></tr>
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<tr><td>log10(<tt>a</tt>)</td><td>log base 10 of <tt>a</tt></td></tr>
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<tr><td>log(<tt>a</tt>,<tt>b</tt>)</td><td>log base <tt>b</tt> of <tt>a</tt></td></tr>
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<tr><td>sqrt(<tt>a</tt>)</td><td>square root</td></tr>
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<tr><td>sin(<tt>a</tt>)</td><td>sine of <tt>a</tt></td></tr>
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<tr><td>cos(<tt>a</tt>)</td><td>cosine of <tt>b</tt></td></tr>
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<tr><td>tan(<tt>a</tt>)</td><td>tangent of <tt>a</tt></td></tr>
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<tr><td>asin(<tt>a</tt>)</td><td>inverse sine of <tt>a</tt></td></tr>
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<tr><td>acos(<tt>a</tt>)</td><td>inverse cosine of <tt>a</tt></td></tr>
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<tr><td>atan(<tt>a</tt>)</td><td>inverse tangent of <tt>a</tt></td></tr>
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<tr><td>to int(<tt>a</tt>)</td><td>convert string <tt>a</tt> to integer</td></tr>
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<tr><td>to real(<tt>a</tt>)</td><td>convert string <tt>a</tt> to real</td></tr>
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<tr><td>to string(<tt>a</tt>)</td><td>convert number <tt>a</tt> to string</td></tr>
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<tr><td>lower(<tt>a</tt>)</td><td>convert string <tt>a</tt> to lower case</td></tr>
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<tr><td>upper(<tt>a</tt>)</td><td>convert string <tt>a</tt> to upper case</td></tr>
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<tr><td>length(<tt>a</tt>)</td><td>length of string <tt>a</tt></td></tr>
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<tr><td>atan2(<tt>y</tt>,<tt>x</tt>)</td><td>inverse tangent of <tt>y</tt>/<tt>x</tt> using the signs of the two arguments to determine the quadrant of the result.</td></tr>
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<tr><td>replace(<tt>a</tt>,<tt>replacethis</tt>,<tt>withthat</tt>)</td><td>replace <tt>replacethis</tt> with <tt>withthat</tt> in string <tt>a</tt></td></td>
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<tr><td>regexp_replace(<tt>a</tt>,<tt>replacethis</tt>,<tt>withthat</tt>)</td><td>replace the regular expression <tt>replacethis</tt> with <tt>withthat</tt> in string <tt>a</tt></td></td>
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<tr><td>substr(<tt>a</tt>,<tt>from</tt>,<tt>len</tt>)</td><td><tt>len</tt> characters of string <tt>a</tt> starting from <tt>from</tt> (first character index is 1)</td></td>
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<tr><td><tt>a</tt> || <tt>b</tt></td><td>concatenate strings <tt>a</tt> and <tt>b</tt></td></tr>
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<tr><td>$rownum</td><td>number current row</td></tr>
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<tr><td>$area</td><td>area of polygon</td></tr>
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<tr><td>$perimeter</td><td>perimeter of polygon</td></tr>
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<tr><td>$length</td><td>area of line</td></tr>
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<tr><td>$id</td><td>feature id</td></tr>
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<tr><td>$x</td><td>x coordinate of point</td></tr>
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<tr><td>$y</td><td>y coordinate of point</td></tr>
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<tr><td>xat(<tt>n</tt>)</td><td>x coordinate of <tt>n</tt>th point of a line (indices start at 0; negative values apply to the last index)</td></tr>
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<tr><td>yat(<tt>n</tt>)</td><td>y coordinate of <tt>n</tt>th point of a line (indices start at 0; negative values apply to the last index)</td></tr>
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<tr><td><tt>a</tt> ^ <tt>b</tt></td><td><tt>a</tt> raised to the power of <tt>b</tt></td></tr>
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<tr><td><tt>a</tt> * <tt>b</tt></td><td><tt>a</tt> multiplied by <tt>b</tt></td></tr>
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<tr><td><tt>a</tt> / <tt>b</tt></td><td><tt>a</tt> divided by <tt>b</tt></td></tr>
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<tr><td><tt>a</tt> + <tt>b</tt></td><td><tt>a</tt> plus <tt>b</tt></td></tr>
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<tr><td><tt>a</tt> - <tt>b</tt></td><td><tt>a</tt> minus <tt>b</tt></td></tr>
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<tr><td>+<tt>a</tt></td><td>positive sign</td></tr>
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<tr><td>-<tt>a</tt></td><td>negative value of <tt>a</tt></td></tr>
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</table>
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