Evaluate a Comparison Expression Without eval(parse())

Parses a string of the form "var op value" and evaluates it directly against a data frame column using operator dispatch. Falls back to column-name lookup for bare names.

Usage

evaluate_comparison(expr, df)

Arguments

expr

Character. An expression like "er <= 0", "size > 35", "grade3 == 1", or a bare column name like "q3.1".

df

Data frame whose columns are referenced by expr.

Value

Logical vector of length nrow(df).

Details

Supported operators (matched longest-first to avoid partial-match ambiguity): <=, >=, !=, ==, <, >.

If no operator is found, expr is treated as a column name and the result is df[[expr]] == 1.

The value on the right-hand side is coerced to numeric when possible, otherwise kept as character for string comparisons.

Examples

if (FALSE) { # \dontrun{
df <- data.frame(er = c(-1, 0, 1, 2), size = c(10, 20, 30, 40))
evaluate_comparison("er <= 0", df)
# [1]  TRUE  TRUE FALSE FALSE

evaluate_comparison("size > 25", df)
# [1] FALSE FALSE  TRUE  TRUE
} # }