Hi,
I'm fairly new to PDL and this seems like an obvious thing to ask about,
but I haven't found it addressed in any docs or FAQs or in this list's
archives.
I'm trying to create piddles from arrays that might include undefined
values and treat those values as bad in further processing. But when
pdl() encounters an input value of undef, it puts a 0 into the piddle.
Setting 0 as the bad value later doesn't work for me because 0 is also a
legitimate data value, and once the piddle is made, there's no
distinguishing an undef treated as 0 from a real 0. (In fact, any float
could be legitimate -- that's why I've been using undef for missing data
-- so experimenting with badvalue was also a dead end.)
Eventually, I came up with this:
use 5.014;
use warnings;
use PDL::LiteF;
# make a piddle where undef becomes BAD
sub pdlify {
my @in = map {ref eq 'ARRAY' ? @$_ : $_} @_;
my @out = map {defined($_) ? pdl($_) : pdl(0)->setbadat(0)} @in;
return cat(@out);
}
This works fine in small-scale tests (my $x = pdlify(1..5,undef,7..10);
say $x; spits out [1 2 3 4 5 BAD 7 8 9 10] as it should), but in
production, one of two things eventually happens:
1) segfault
2) cat: unknown error from the internals:
PDL: Problem with assignment: PDL:Internal Error: data structure recursion
limit exceeded (max 1000 levels)
This could mean that you have found an infinite-recursion error in
PDL, or
that you are building data structures with very long dataflow
dependency
chains. You may want to try using sever() to break the
dependency.
Each call to pdlify is acting on a fresh list of scalars (all numbers or
undef), so there shouldn't be any dependencies to speak of at this point.
Bottom line, is there an idiom or package already out there that will take
a list and create a piddle where undefined input values are represented as
BAD rather than 0, or is there at least some way to do it that doesn't go
down some mysterious recursive rabbit hole?
Thanks.
-- Erich
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