Dear PDL'ers,
I am stuck with an apparently simple problem and hoped that someone in
this list might have a clue.
I have approx. 130000 pairs of data, z and r, which represent
observations of some function r at some coordinate z.
A sample of the data looks like this:
z r
3311 311.817
3346 249.333
3238 353.368
3279 367.020
3347 324.405
3448 274.632
3161 310.469
3204 358.739
...... ......
These observations come from a three dimensional space, and therefore
there exists more than one r value for each value of the coordinate z.
What I want to do is to estimate a gross distribution of r values
versus z. Simple as it seems I am having troubles to set up a PDL code
to compute it.
My thought is: first compute bins (hist) of the z variable and then
find all r observations that fit within intervals (z - delta_z; z
+delta_z), over the whole range of z. Finally find the average,
maximum and distribution of r values over that interval.
The idea was to create a 2D piddle where the rows are values of r and
the columns are the values of z bins. Then, by some suitable
transposing, obtain the r values using which and index. As I could not
make this work, I tried with the less fancy approach of doing a loop
with 1D piddles. My (still not working) version of the solution is:
use PDL;
use PDL::NiceSlice;
use PDL::Graphics::PGPLOT;
# read data into two piddles
my ($z,$r) = rcols ('data');
# calculates bins of size 10 from $z values between minimum and maximum
my ($zv,$zfs) = hist($z, int (min $z), int (max $z), 10);
# defines auxiliary variables
# lower limit of bin
my $zvl = $zv - 5;
# upper limit of bin
my $zvu = $zv + 5;
# an empty piddle to allocate the aggregated observations
# its dimensions are those of the binned z values
my $ri = zeroes(nelem($zv));
# a temporary piddle
# its dimensions are those of the original data
my $tmp = zeroes(nelem($z));
# sets an index variable to 0
my $i = 0;
# starts the loop
while ($i < nelem($zv)) {
# finds the indexes of z elements that fit within the interval,
# captures the r values at the same locations and stores that in the temp piddle
$tmp .= $r->index(which($z > $zvl($i) | $z < $zvu($i) ));
# calculates some statistics
$ri($i) .= average ($tmp);
$i++;
}
# plots ...
points zv,$ri;
This doesn't work though and neither did its many sibling versions. I
am stuck and perplexed.
Any hint will be appreciated!
Thanks!
Hernán
--
Hernán De Angelis
Linux user # 397217
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