I'm trying to simulate the effects of spectral pileup in a detector.
Incoming event are transformed into a pseudo-Gaussian shaped signal
(f(t)). If two or more events occur too close together their signals
overlap.
As a prototype I thought I could use the range operator to construct
views onto a piddle that would allow me to easily add overlapping
signals.
For example, given
$ph : the signal function with dimension [$nsample]
$t: the arrival time of events with dimension [$nevents]
$buffer: the coadded signals
Then
$bp = $buffer->range($t->transpose,$nsample)->transpose;
is a set of $nsample windows onto $buffer, some of which may overlap.
Theoretically I could then perform
$bp += $ph
and $buffer would contain the coadded signals. Alas, this doesn't seem
to work. Here's an abstracted example
$z = xvals(20);
$v = $z->range( pdl( 1,8 )->transpose, 9 )->transpose;
p $z
[0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19]
p $v
[
[ 1 2 3 4 5 6 7 8 9]
[ 8 9 10 11 12 13 14 15 16]
]
So, $v is a set of two overlapping windows onto $z. But,
$v += 1;
p $v
[
[ 2 3 4 5 6 7 8 9 10]
[ 9 10 11 12 13 14 15 16 17]
]
p $z
[0 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 17 18 19]
The addition is only done once per element in $z, not once per element
in $v. I expected $v to look like this:
[
[ 2 3 4 5 6 7 8 10 11]
[10 11 11 12 13 14 15 16 17]
]
and thus for $z to look like this
[0 2 3 4 5 6 7 8 10 11 11 12 13 14 15 16 17 17 18 19]
Bug or feature?
Thanks,
Diab
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