ifelse {base} | R Documentation |
ifelse
returns a value with the same shape as
test
which is filled with elements selected
from either yes
or no
depending on whether the element of test
is TRUE
or FALSE
.
ifelse(test, yes, no)
test |
an object which can be coerced to logical mode. |
yes |
return values for true elements of |
no |
return values for false elements of |
If yes
or no
are too short, their elements are recycled.
yes
will be evaluated if and only if any element of test
is true, and analogously for no
.
Missing values in test
give missing values in the result.
A vector of the same length and attributes (including dimensions and
"class"
) as test
and data values from the values of
yes
or no
. The mode of the answer will be coerced from
logical to accommodate first any values taken from yes
and then
any values taken from no
.
The mode of the result may depend on the value of test
(see the
examples), and the class attribute (see oldClass
) of the
result is taken from test
and may be inappropriate for the
values selected from yes
and no
.
Sometimes it is better to use a construction such as
(tmp <- yes; tmp[!test] <- no[!test]; tmp), possibly extended to handle missing values in
test
.
Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.
if
.
x <- c(6:-4) sqrt(x) #- gives warning sqrt(ifelse(x >= 0, x, NA)) # no warning ## Note: the following also gives the warning ! ifelse(x >= 0, sqrt(x), NA) ## example of different return modes: yes <- 1:3 no <- pi^(0:3) typeof(ifelse(NA, yes, no)) # logical typeof(ifelse(TRUE, yes, no)) # integer typeof(ifelse(FALSE, yes, no)) # double