eval Function (GPL)
Syntax
eval(<expression>)
<expression>. A mathematical expression, such as log(salary)
.
Description
Evaluates a mathematical expression for each case in the data.
You can use many different mathematical functions in the expression.
See the topic eval Operators and Functions (GPL) for more information. If needed, you can wrap
the result of a function in another function. Therefore, datetostring(date())
is
a valid expression.
The eval
function is also useful for evaluating
a Boolean expression whose result can be used in the summary.countTrue
, summary.percentTrue
,
and summary.proportionTrue
functions. This combination
allows you to plot the number or percent of cases greater than or
less than a specific value.
Examples
TRANS: saldiff = eval(salary-salbegin)
ELEMENT: point(position(summary.mean(jobcat*saldiff)))
DATA: x = iter(-100,100,1)
TRANS: y = eval(x**2)
ELEMENT: line(position(x*y))
TRANS: salGreaterThan = eval(salary>50000)
ELEMENT: interval(position(summary.percentTrue(jobcat*salGreaterThan)))