interpChar {Ecfun}  R Documentation 
For x
and y
logical, integer,
numeric, Date or POSIX:
xOut < x*(1.proportion) + y*.proportion
Otherwise, coerce to character and return a
substring
of x
or y
with number of characters interpolating linearly
between nchar(x)
and nchar(y)
;
see details.
*** NOTE: This function is currently in flux. The results may not match the documentation and may change in the future.
The current version does character interpolation on the cumulative number of characters with defaults with only one argument that may not be easy to understand and use. Proposed:
old: interpolate on
number of characters in each string with the
default for a missing argument being
character(length(x))
[or
character(length(y))
or
numeric(length(x))
or ...]
20140808: default with either x or y missing
should be to set the other to the one we have,
so interpChar
becomes a no op – except
that values with .proportion
outside
(validProportion
= [0, 1] by default)
should be dropped.
interpChar(x, ...)
## S3 method for class 'list'
interpChar(x, .proportion,
argnames=character(3),
message0=character(0), ...)
## Default S3 method:
interpChar(x, y, .proportion,
argnames=character(3),
message0=character(0), ...)
x 
either a vector or a list. If a list, pass
the first two elements as the first two
arguments of 
y 
a vector 
.proportion 
A number or numeric vector assumed to be between 0 and 1. 
argnames 
a character vector of length 3 giving
arguments 
message0 
A character string to be passed with

... 
optional arguments for

1. x
, y
and .proportion
are first compared for compatible lengths using
compareLengths
. A warning is
issued if the lengths are not compatible. They
are then all extended to the same length using
rep
.
2. If x
and y
are both numeric,
interpChar
returns the standard linear
interpolation (described above).
3. If x
, y
, and .proportion
are all provided with at least one of x
and y
not being numeric or logical, the
algorithm does linear interpolation on the
difference in the number of characters between
x
and y
. It returns characters
from y
except when nchar(x)
>
nchar(y)
, in which case it returns
characters from x
. This meets the end
conditions that the number of characters matches
that of x
when .proportion
is 0
and matches that of y
when
.proportion
is 1. This can be used to
"erase" characters moving from one frame to
the next in a video. See the examples.
4. If either x
or y
is missing,
it is replaced by a default vector of the same
type and length; for example, if y
is
missing and x
is numeric, y
=
numeric(length(x))
. (If the one supplied
is not numeric or logical, it is coerced to
character.)
A vector: Numeric if x
and y
are
both numeric and character otherwise. The length
= max length of x
, y
, and
.proportion
.
Spencer Graves
interpPairs
, which calls
interpChar
classIndex
, which is called by
interpChar
to help decide the class of
the interpolant.
##
## 1. numerics
##
# 1.1. standard
xNum < interpChar(1:3, 4:5, (0:3)/4)
# answer
xN. < c(1, 2.75, 3.5, 4)
all.equal(xNum, xN.)
# 1.2. list of length 1 with a numeric vector:
# return that vector with a warning
xN1 < interpChar(list(a.0=1:4), .5)
# answer
xN1. < 1:4
all.equal(xN1, xN1.)
##
## 2. Single character vector
##
i.5 < interpChar(list(c('a', 'bc', 'def')), .p=0.3)
# If cumulative characters:
# 0.3*(total 6 characters) = 1.8 characters
#
# However, the current code does something different,
# returning "a", "bc", "d" < like using 1.p?
# This is a problem with the defaults with a single
# argument; ignore this issue for now.
# 20140604
i.5. < c('a', 'b', '')
#all.equal(i.5, i.5.)
##
## 3. Reverse character example
##
i.5c < interpChar(c('a', 'bc', 'def'), '', 0.3)
# check: 0.7*(total 6 characers) = 4.2 characters
i.5c. < c('a', 'bc', 'd')
all.equal(i.5c, i.5c.)
# The same thing specified in a list
i.5d < interpChar(list(c('a', 'bc', 'def'), ''), 0.3)
all.equal(i.5d, i.5c.)
##
## 4. More complicated example
##
xCh < interpChar(list(c('Do it', 'with R.')),
c(0, .5, .9))
# answer
xCh. < c('', 'with', 'Do ')
# With only one input, it's assumed to be y.
# It is replicated to length(.proportion),
# With nchar = 5, 7, 5, cum = 5, 12, 17.
all.equal(xCh, xCh.)
##
## 5. Still more complicated
##
xC2 < interpChar(c('a', 'fabulous', 'bug'),
c('bigger or', 'just', 'big'),
c(.3, .3, 1) )
# answer
x.y.longer < c('bigger or', 'fabulous', 'big')
# use y with ties
# nch smaller 1 4 3
# nch larger 9 8 3
# d.char 8, 4, 0
# cum characters 8, 12, 12
# prop .3, .7, 1
# prop*12 3.6, 8.4, 12
# cum.sm 1, 5, 8
# cum.sm+prop*12 5, 13, 20
# cum(larger[1]) 5, 4, 3
xC2. < c('bigge', 'fabu', 'big')
all.equal(xC2, xC2.)
##
## 6. with one NULL
##
null1 < interpChar(NULL, 1, 1)
all.equal(null1, 1)
null2 < interpChar('abc', NULL, .3)
all.equal(null2, 'ab')
##
## 7. length=0
##
log0 < interpChar(logical(0), 2, .6)
all.equal(log0, 1.2)
##
## 8. Date
##
##
## 9. POSIXct
##