| Extract {hyper2} | R Documentation |
Extract or replace parts of a hyper2 object
## S3 method for class 'hyper2' x[...] ## S3 replacement method for class 'hyper2' x[index, ...] <- value assign_lowlevel(x,index,value) overwrite_lowlevel(x,value)
x |
An object of class |
... |
Further arguments, currently ignored |
index |
A list with integer vector elements corresponding to the brackets whose power is to be replaced |
value |
Numeric vector of powers |
These methods should work as expected, although the off-by-one issue might be a gotcha.
For the extract method, a numeric vector is returned but the elements may be in any order (the brackets and indeed the powers are not stored in any particular order).
The replace method, H[L] <- value, the index L is a list
specifying the brackets to be overwritten; argument value is not
recycled unless it is of length 1.
If the index argument is missing, viz H1[] <- H2, this is a
special case. Argument H1 must be a hyper2 object, and
the idiom effectively executes H1[brackets(H2)] <- powers(H2),
but more efficiently (note that this operation is well-defined even
though the order of the brackets is arbitrary). This special case is
included in the package because it has a very natural C++
expression [function overwrite() in the src/ directory]
that was too neat to omit.
Altering (incrementing or decrementing) the power of a single bracket
is possible using idiom like H[x] <- H[x] + 1; this is
documented at Ops.hyper2, specifically
hyper2_sum_numeric() and a discussion is given at
increment.Rd.
Functions assign_lowlevel() and overwrite_lowlevel() are
low-level helper functions and not really intended for the end-user.
The extractor method returns a hyper2 object, restricted to the
elements specified
Use powers() and brackets() to extract a numeric vector of
powers or a list of integer vectors respectively.
Replacement idiom H[x] <- val cannot use non-trivial recycling.
This is because the elements of H are stored in an arbitrary
order, but the elements of val are stored in a particular order.
Also see function hyper2_sum_numeric().
Robin K. S. Hankin
data(chess)
chess["Topalov"]
chess[c("Topalov","Anand")]
chess[c("Anand","Topalov")]
# Topalov plays Anand and wins:
chess["Topalov"] <- chess["Topalov"]+1
chess[c("Topalov","Anand")] <- chess[c("Topalov","Anand")]-1
# Topalov plays *Kasparov* and wins:
chess["Topalov"] %<>% inc
chess[c("Topalov","Kasparov")] %<>% dec
# overwriting idiom:
H <- hyper2(list("Topalov","X"),6)
chess[] <- H