| 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 test. |
no |
return values for false elements of test. |
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 giving missing values in the result.
A vector of the same length and attributes (including
class) as test and data values from the values of
yes or no. The mode of the answer will be coerced to
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, and the
class attribute 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)