Utility functions to verify an objects's properties including whether it is a scalar or vector,
the class, the length, and (if numeric) whether the range of values is on a specified interval. Additionally,
the checkLengths
function can be used to ensure that all the supplied inputs have equal lengths.
1 2 3 4 5 6  isInteger(x)
checkScalar(x, isType = "numeric", ...)
checkVector(x, isType = "numeric", ..., length=NULL)
checkRange(x, interval = 0:1, inclusion = c(TRUE, TRUE),
varname = deparse(substitute(x)), tol=0)
checkLengths(..., allowSingle=FALSE)

x 
any object. 
isType 
character string defining the class that the input object is expected to be. 
length 
integer specifying the expected length of the object in the case it is a vector. If 
interval 
twoelement numeric vector defining the interval over which the input object is expected to be contained.
Use the 
inclusion 
twoelement logical vector defining the boundary behavior of the specified interval. A 
varname 
character string defining the name of the input variable as sent into the function by the caller.
This is used primarily as a mechanism to specify the name of the variable being tested when 
tol 
numeric scalar defining the tolerance to use in testing the intervals of the

... 
For the

allowSingle 
logical flag. If 
isInteger
is similar to is.integer
except that isInteger(1)
returns TRUE
whereas is.integer(1)
returns FALSE
.
checkScalar
is used to verify that the input object is a scalar as well as the other properties specified above.
checkVector
is used to verify that the input object is an atomic vector as well as the other properties as defined above.
checkRange
is used to check whether the numeric input object's values reside on the specified interval.
If any of the values are outside the specified interval, a FALSE
is returned.
checkLength
is used to check whether all of the supplied inputs have equal lengths.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32  # check whether input is an integer
isInteger(1)
isInteger(1:5)
try(isInteger("abc")) # expect error
# check whether input is an integer scalar
checkScalar(3, "integer")
# check whether input is an integer scalar that resides
# on the interval on [3, 6]. Then test for interval (3, 6].
checkScalar(3, "integer", c(3,6))
try(checkScalar(3, "integer", c(3,6), c(FALSE, TRUE))) # expect error
# check whether the input is an atomic vector of class numeric,
# of length 3, and whose value all reside on the interval [1, 10)
x < c(3, pi, exp(1))
checkVector(x, "numeric", c(1, 10), c(TRUE, FALSE), length=3)
# do the same but change the expected length; expect error
try(checkVector(x, "numeric", c(1, 10), c(TRUE, FALSE), length=2))
# create faux function to check input variable
foo < function(moo) checkVector(moo, "character")
foo(letters)
try(foo(1:5)) # expect error with function and argument name in message
# check for equal lengths of various inputs
checkLengths(1:2, 2:3, 3:4)
try(checkLengths(1,2,3,4:5)) # expect error
# check for equal length inputs but ignore single element vectors
checkLengths(1,2,3,4:5,7:8, allowSingle=TRUE)

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