On Apr 26, 2009, at 7:48 AM, Esmail wrote:
Hello David,
Let me try again, I don't think this was the best post ever I've
made :-)
Hopefully this is clearer, or otherwise I may break this up into
three separate simple queries as this may be too long.
> "==" is not an assignment operator in R, so the answer is that it
> would do neither. "<-" and "=" can do assignment. In neither case
> would it be a "deep copy".
It was late when I posted the code, I made a mistake with regard to
the assignment operator and used the boolean compare instead -- thanks
for catching that.
It should have been:
keep_pop[1:POP_SIZE] = pop[1:POP_SIZE]
-------- Here's an edited and clearer version I hope:
The basic idea is that I am trying to keep track of a number of
bitrings.
Therefore I am creating a matrix (named 'pop') whose rows are made up
of bit vectors (ie my bitstrings). I only initialize half of the rows
with my bitstrings of random 1s and 0s, the rest of the rows are set
to all zeros).
So I use following function call to create a matrix and fill it with
bit strings:
pop=create_pop_2(POP_SIZE, LEN)
where
POP_SIZE refers to the number of rows
LEN to the columns (length of my bitstrings)
This is the code I call:
####################################################
# create a random binary vector of size "len"
#
create_bin_Chromosome <- function(len)
{
sample(0:1, len, replace=T)
}
############## create_population ###################
# create population of chromosomes of length len
# the matrix contains twice as much space as popsize
#
create_pop_2 <- function(popsize, len)
{
datasize=len*popsize
print(datasize)
npop <- matrix(0, popsize*2, len, byrow=T)
for(i in 1:popsize)
npop[i,] = create_bin_Chromosome(len)
npop
}
My 3 questions:
(1) If I did
keep_pop[1:POP_SIZE] = pop[1:POP_SIZE]
to keep a copy of the original data structure before manipulating
'pop' potentially, would this make a deep copy or just shallow? Ie
if I change something in pop would keep_pop change too? I would
like two independent copies so that 'keep_pop' stays intact while
'pop' may change.
> "<-" and "=" can do assignment. In neither case would it be a
> "deep copy".
Is there a deepcopy operator, or would I have to have two nested
loops and iterate through them? Or is there a nice R-idiomatic way
to do this?
Not that I know of, although my knowledge of R depth is not
encyclopedic. You might get the desired sort of effect by creating a
copy inside a function, working on it inside the function in the
manner desired, and then comparing the output to the original. There
might be other strategies to get certain effects by creating specific
environments.
(2) If I wanted to change the order of rows in my matrix 'pop', is
there an easy way to shuffle these? I.e., I don't want to change
any of the bitstrings vectors/rows, just the order of the rows in
the
matrix 'pop'. (E.g., in Python I could just say something like
suffle(pop)) - is there an equivalent for R?
So if pop [ [0, 0, 0]
[1, 1, 1]
[1, 1, 0] ]
after the shuffle it may look like
[ [1, 1, 0] (originally at index 2)
[1, 1, 1] (originally at index 1)
[0, 0, 0] ] (originally at index 0)
the rows themselves remained intact, just their order changes.
This is a tiny example, in my case I may have 100 rows (POPS_SIZE)
and rows of LEN 200.
Yes. As I said before "I am going to refrain from posting speculation
until you provide valid R code
that will create an object that can be the subject of operations."
(3) I would like to compare the contents of 'keep_pop' (a copy of the
original 'pop') with the current 'pop'. Though the order of rows
may be different between the two, it should not matter as long as
the same rows are present. So for the example given above, the
comparison should return True.
For instance, in Python this would be simply
if sorted(keep_pop) == sorted(pop):
print 'they are equal'
else
print 'they are not equal'
Is there an equivalent R code segment?
If you created a random index vector that was used to sort the rows
for display or computational purposes only, you could maintain the
original ordering so that row wise comparisons could be done.
I hope this post is clearer than my original one. Thank you David for
pointing out some of the shortcomings of my earlier post.
Thanks,
Esmail
David Winsemius, MD
Heritage Laboratories
West Hartford, CT
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