Comparison
Relational Operators
Binary operators which allow the comparison of values in atomic vectors.
 Keywords
 logic
Usage
x < y
x > y
x <= y="" x="">= y
x == y
x != y
Arguments
 x, y
 atomic vectors, symbols, calls, or other objects for which methods have been written.
Details
The binary comparison operators are generic functions: methods can be
written for them individually or via the
Ops
) group generic function. (See
Ops
for how dispatch is computed.)
Comparison of strings in character vectors is lexicographic within the
strings using the collating sequence of the locale in use: see
locales
. The collating sequence of locales such as
en_US is normally different from C (which should use
ASCII) and can be surprising. Beware of making any assumptions
about the collation order: e.g. in Estonian Z
comes between
S
and T
, and collation is not necessarily
characterbycharacter  in Danish aa
sorts as a single
letter, after z
. In Welsh ng
may or may not be a single
sorting unit: if it is it follows g
. Some platforms may
not respect the locale and always sort in numerical order of the bytes
in an 8bit locale, or in Unicode codepoint order for a UTF8 locale (and
may not sort in the same order for the same language in different
character sets). Collation of nonletters (spaces, punctuation signs,
hyphens, fractions and so on) is even more problematic.
Character strings can be compared with different marked encodings
(see Encoding
): they are translated to UTF8 before
comparison.
At least one of x
and y
must be an atomic vector, but if
the other is a list R attempts to coerce it to the type of the atomic
vector: this will succeed if the list is made up of elements of length
one that can be coerced to the correct type.
If the two arguments are atomic vectors of different types, one is coerced to the type of the other, the (decreasing) order of precedence being character, complex, numeric, integer, logical and raw.
Missing values (NA
) and NaN
values are
regarded as noncomparable even to themselves, so comparisons
involving them will always result in NA
. Missing values can
also result when character strings are compared and one is not valid
in the current collation locale.
Language objects such as symbols and calls are deparsed to character strings before comparison.
Value

A logical vector indicating the result of the element by element
comparison. The elements of shorter vectors are recycled as
necessary.Objects such as arrays or timeseries can be compared this way
provided they are conformable.
Note
Do not use ==
and !=
for tests, such as in if
expressions, where you must get a single TRUE
or
FALSE
. Unless you are absolutely sure that nothing unusual
can happen, you should use the identical
function
instead.
For numerical and complex values, remember ==
and !=
do
not allow for the finite representation of fractions, nor for rounding
error. Using all.equal
with identical
is almost
always preferable. See the examples.
S4 methods
These operators are members of the S4 Compare
group generic,
and so methods can be written for them individually as well as for the
group generic (or the Ops
group generic), with arguments
c(e1, e2)
.
References
Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.
Collation of character strings is a complex topic. For an introduction see http://en.wikipedia.org/wiki/Collating_sequence. The Unicode Collation Algorithm (http://unicode.org/reports/tr10/) is likely to be increasingly influential. Where available R makes use of ICU (http://site.icuproject.org/ for collation.
See Also
factor
for the behaviour with factor arguments.
Syntax
for operator precedence.
icuSetCollate
to tune the string collation algorithm
when ICU is in use.
Examples
library(base)
x < stats::rnorm(20)
x < 1
x[x > 0]
x1 < 0.5  0.3
x2 < 0.3  0.1
x1 == x2 # FALSE on most machines
identical(all.equal(x1, x2), TRUE) # TRUE everywhere
# range of most 8bit charsets, as well as of Latin1 in Unicode
z < c(32:126, 160:255)
x < if(l10n_info()$MBCS) {
intToUtf8(z, multiple = TRUE)
} else rawToChar(as.raw(z), multiple= TRUE)
## by number
writeLines(strwrap(paste(x, collapse=" "), width = 60))
## by locale collation
writeLines(strwrap(paste(sort(x), collapse=" "), width = 60))