For values at the extremeties of an instrument’s range of measurement, the Online Information System might send RippleDown a value such as “< 1” or “> 10”. Results like this are not numbers, but need to be treated as such for most purposes. In rule conditions, RippleDown converts values like these to numbers very close to the limit value (within 5 decimal places), but greater or less than, as appropriate. For example, the value “< 1” is treated as the number 0.99999, and the value “> 10” is treated as the
number 10.00001.
For example, given the following case fragment,
Urea [2.5 - 7.5] 7.3 > 9 7.4 Digoxin [1.0 - 2.6] 1.1 0.8 < 0.1
The following conditions are all true:
max Urea > 8
max Urea > 9
second most recent Urea is high
Digoxin is low
Digoxin < 0.1
Digoxin < 0.2
Digoxin is numeric
Note: A side effect of converting values like “< x” or ” > y” to a number is that conditions like
second most recent Urea > 10,
Digoxin < 0.05
will evaluate as false.