stopifnot                package:base                R Documentation

Ensure the 'Truth' of R Expressions

Description:

     If any of the expressions in '...' are not 'all' 'TRUE', 'stop' is
     called, producing an error message indicating the _first_ of the
     elements of '...' which were not true.

Usage:

     stopifnot(...)

Arguments:

     ...: any number of ('logical') R expressions, which should
          evaluate to 'TRUE'.

Details:

     This function is intended for use in regression tests or also
     argument checking of functions, in particular to make them easier
     to read.

     'stopifnot(A, B)' is conceptually equivalent to '{
     if(any(is.na(A)) || !all(A)) stop(...) ; if(any(is.na(B)) ||
     !all(B)) stop(...) }'.

Value:

     ('NULL' if all statements in '...' are 'TRUE'.)

See Also:

     'stop', 'warning'.

Examples:

     stopifnot(1 == 1, all.equal(pi, 3.14159265), 1 < 2) # all TRUE

     m <- matrix(c(1,3,3,1), 2,2)
     stopifnot(m == t(m), diag(m) == rep(1,2)) # all(.) |=>  TRUE

     op <- options(error = expression(NULL))
     # "disable stop(.)"  << Use with CARE! >>

     stopifnot(all.equal(pi, 3.141593),  2 < 2, all(1:10 < 12), "a" < "b")
     stopifnot(all.equal(pi, 3.1415927), 2 < 2, all(1:10 < 12), "a" < "b")

     options(op)# revert to previous error handler

