Enables the aggregation of arbitrary distance measures using a Java snippet. The port number is used to refer to a value of a given distance measure for example $${D:Port_0}$$ will insert the double value resulting of the distance measure on port 0.

Examples:

Compute the arithmetic mean of the distance measures on port 0 and 1:
mean($${D:Port_0}$$,$${D:Port_1}$$)

Compute the arithmetic mean of the distance measures on port 0 and 1 only if the distance on port 0 is less or equal to 0.5 and return 1 otherwise
ifElse($${D:Port_0}$$ <= 0.5, mean($${D:Port_0}$$, $${D:Port_1}$$), 1)

Note that strings which are part of the expression and are not from the input data (or the result of another wrapped function call) need to be enclosed in double quotes ('"'). Additionally, if the string contains a quote character, it must be escaped using a backslash character ('\"'). Finally, other special characters such as single quotes and backslashes need to be escaped using a backslash. For instance, a single backslash in a string is written as two consecutive backslash characters; the first one acts as the escape character for the second.