Building LimeSurvey Expression Manager equations

These are a set of really basic functions that facilitate building LimeSurvey Expression Manager (LSEM) equations.

ls_eq_build(lhs, operator, rhs)

ls_eq_is(varCode, value, naok = TRUE)

ls_eq_isChecked(varCode, naok = TRUE)

ls_eq_isUnchecked(varCode, naok = TRUE)

ls_eq_if(cond, ifExpr, elseExpr)

ls_eq_ifRegex(regex, varCode, ifExpr, elseExpr, naok = TRUE)

ls_eq_brace(expr)

ls_eq_quote(expr)

Arguments

lhs

The left-hand side expression.

operator

The operator.

rhs

The right-hand side expression.

varCode

A LimeSurvey variable code.

value

A value.

naok

Whether to append ".NAOK" to the variable code.

cond

A condition, for example created by ls_eq_build() or ls_eq_is().

ifExpr, elseExpr, expr

An expression.

regex

A regular expression.

Value

A character vector.

Details

ls_eq_build() just pastes together its three arguments in the same order using a space as separator. So it's mostly used for clarity when building LSEM equations.

ls_eq_is() uses ls_eq_build() to specify a logical expression that is true when varCode equals value.

ls_eq_if() builds an if/then/else expression; if cond evaluates to TRUE, the LSEM uses ifExpr; otherwise, it uses elseExpr.

ls_eq_ifRegex checks a question against a regular expression.

ls_eq_isChecked() and ls_eq_isUnchecked() return an expression evaluating whether a checkbox is checked (or not).

ls_eq_brace() simply embraces expr, an expression (i.e. it prepends { and appends }).

ls_eq_quote() simply embraces expr, an expression (i.e. it prepends ' and appends ').

Examples

ls_eq_build("questionCode", "==", "Y");
#> [1] "questionCode == Y"