Expressions are formulas based on the attributes in the project, and may contain operators such as * or /, and other key words such as “previous” or “last”. Expressions are evaluated on the current case, giving a textual or numeric value that may be used in a comment, or as the value of a Calculated Value attribute.
The simplest type of expression is an attribute name, e.g. “cholesterol”. The value of such an expression will be the value of the current sample for that attribute in the case.
Some examples of expressions are:
cholesterol
previous cholesterol
AST / ALT
Expressions can be inserted into a comment, for example, to refer to some significant test result or date from the case. See “Inserting a variable expression into a comment“. Expressions are also used when searching for cases that satisfy some condition. See “Searching for cases that satisfy a condition“.
To create an expression, type it directly into the Expression area. If you select an attribute from the list, it will be copied into the Expression area so you don’t have to type it.
As soon as you have entered a valid expression, a confirmation status message will appear. If there is a case currently showing, the status message will show the value of your expression evaluated for this case.
See also:Using brackets in expressions