Marek-
I've opened a highest priority bug report based on your information:
http://sourceforge.net/p/pdl/bugs/390
Could you add information on your system specifics to the ticket
for reference (the output of perldl -V has the main information)?
We'll be updating the ticket as information becomes available.
Thanks for reporting the problem!
Chris
On 6/16/2015 09:49, Marek Gierliński wrote:
This is very bad news for me. I just searched through my scripts and
found 586 instances of 'stats'. If this is not corrected, I have to
assume that all of them might potentially produce incorrect results,
without even failing (like in the if($s > 0) example).
We've been using 2.007 for a couple of months now. I'm not even sure
if my recent results are correct.
Marek
On Tue, 16 Jun 2015 at 14:43 Chris Marshall <devel.chm...@gmail.com
<mailto:devel.chm...@gmail.com>> wrote:
That definitely seems like a bug to me. Thanks for the
cross-check, Marek.
Devels, I see the same in the latest PDL release so it is not a
PDL-2.007 only issue.
--Chris
On 6/16/2015 09:36, Marek Gierliński wrote:
OK, thank you for your explanations. I'm not sure if all of this
makes sense. If you try
print $s > 5;
in the above example, you will get 'BAD'. 5 is just a scalar and
not a bad value. And $s is a one-dimensional piddle with a value
different from the bad value. Neither of the values in this
conditional expression is bad. Why does it return a string 'BAD'?
Marek
On Tue, 16 Jun 2015 at 14:24 Chris Marshall
<devel.chm...@gmail.com <mailto:devel.chm...@gmail.com>> wrote:
This result seems to violate the principle of least surprise.
On the LHS we have a PDL with badvalue(0) and on the RHS we
have a perl scalar with value 0 (which happens to be the bad
value for the PDL).
It seems surprising that $pdl > 0 is actually $pdl >
pdl(0)->badvalue(0)
Thoughts?
Chris
-------- Forwarded Message --------
Subject: Re: [Pdl-general] Weird behaviour of stats with bad
values
Date: Tue, 16 Jun 2015 09:18:29 -0400
From: Chris Marshall <devel.chm...@gmail.com>
<mailto:devel.chm...@gmail.com>
To: Derek Lamb <de...@boulder.swri.edu>
<mailto:de...@boulder.swri.edu>, Marek Gierliński
<marek.gierlin...@gmail.com> <mailto:marek.gierlin...@gmail.com>
CC: pdl-gene...@lists.sourceforge.net
<mailto:pdl-gene...@lists.sourceforge.net>
I think the problem is that if $s is a badvalue piddle with
the badvalue=0
then $s>0 is $s>BAD which is BAD. If you use a value for
badvalue that is
not in the comparison, you should be good.
--Chris
On 6/16/2015 09:11, Derek Lamb wrote:
Thanks for the simple example. That helps a lot.
The actual problem is that piddles with the badflags set
always evaluate to BAD when element-wise logical operations
are performed on them.
"print $s<0" prints BAD instead of 0 or 1. "print $x>0"
also prints [BAD BAD BAD BAD].
$m and $s have their badflags set (as they should, since
they were made from partially-bad data). You can check if
they can be safely cleared, and clear them if so, with
$s->check_badflag, etc. Since $m and $s are 1-element
piddles, you can also just set them directly to their scalar
values, for example
map{$_=$_->sclr} ($m,$s)=stats($x); #if you know they are
only going to be 1 element piddles
OR
map{$_=$_->((0))} ($m,$s)=stats($x); #if you just want the
first value
The fact that $m and $s are 1-element piddles is likely what
is causing your problem. My guess is that this behavior has
changed (perhaps intentionally, perhaps not) between your
old version and more recent versions, and if you were
getting $m and $s as simple perl scalars before you would
not have seen this problem. I can verify that stats() has
returned 1-piddles and not perl scalars at least as far back
as PDL-2.4.11.
cheers,
Derek
On Jun 16, 2015, at 6:29 AM, Marek Gierliński
<marek.gierlin...@gmail.com
<mailto:marek.gierlin...@gmail.com>> wrote:
Oops, sorry, I missed a line when copying the text. Here is
the code again.
use PDL;
use PDL::NiceSlice;
my $x = pdl(1, 2, 3, 0);
$x->badflag(1);
$x->badvalue(0);
print "x = $x\n";
my ($m, $s) = stats($x);
print "m = $m, s = $s\n";
print "s greater than zero\n" if $s > 0;
print "s less than zero\n" if $s < 0;
print "s equals zero\n" if $s == 0;
On Tue, 16 Jun 2015 at 12:20 Chris Marshall
<devel.chm...@gmail.com <mailto:devel.chm...@gmail.com>> wrote:
Hi Marek-
Do you have a complete example showing the problem?
You don't show where $m and $s are being set below.
Thanks,
Chris
On 6/16/2015 07:04, Marek Gierliński wrote:
I have recently encountered a weird problem with stats
(or statsover) using bad values. The resulting numbers
have a strange property, they always return true in
comparisons. This code:
use PDL;
use PDL::NiceSlice;
my $x = pdl(1, 2, 3, 0);
$x->badflag(1); $x->badvalue(0);
print "m = $m, s = $s\n";
print "s greater than zero\n" if $s > 0;
print "s less than zero\n" if $s < 0;
print "s equals zero\n" if $s == 0;
returns the following output:
x = [1 2 3 BAD]
m = 2, s = 1
s greater than zero
s less than zero
s equals zero
which doesn't make any sense. Can anyone explain this?
I always assumed that 'stats' returned ordinary Perl
scalars, but this must be something different.
I'm using PDL version 2.007. We had an older version
installed for a long time and I think this problem
appeared when we upgraded to 2.007.
Marek
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