W. eWatson wrote:
tom wrote:
W. eWatson wrote:
The other night I surveyed a site for astronomical use by measuring
the altitude (0-90 degrees above the horizon) and az (azimuth, 0
degrees north clockwise around the site to 360 degrees, almost north
again) of obstacles, trees. My purpose was to feed this profile of
obstacles (trees) to an astronomy program that would then account for
not sighting objects below the trees.
When I got around to entering them into the program by a file, I
found it required the alt at 360 azimuth points in order from 0 to
360 (same as 0). Instead I have about 25 points, and expected the
program to be able to do simple linear interpolation between those.
Is there some simple operational device in Python that would allow me
to create an array (vector) of 360 points from my data by
interpolating between azimuth points when necessary? All my data I
rounded to the nearest integer. Maybe there's an interpolation operator?
As an example, supposed I had made 3 observations: (0,0) (180,45) and
(360,0). I would want some thing like (note the slope of the line
from 0 to 179 is 45/180 or 0.25):
alt: 0, 0.25, 0.50, 0.75, ... 44.75, 45.0
az : 0, 1, 2, 3, 180
Of course, I don't need the az.
If I understand you right, I think using interpolation as provided by
scipy would do what you need.
Here's an example:
from scipy.interpolate.interpolate import interp1d
angles = [0, 22, 47.5, 180, 247.01, 360]
altitudes = [18, 18, 26, 3, 5, 18]
desired_angles = range(0, 361)
skyline = interp1d(angles, altitudes, kind="linear")
vals = skyline(desired_angles)
# that is, vals will be the interpolated altitudes at each of the
# desired angles.
if 1: # plot this out with matplotlib
import pylab as mx
mx.figure()
mx.plot(angles, altitudes, 'x')
mx.plot(desired_angles, vals)
mx.show()
I decided this morning and roll up my sleeves and write the program. I
plan to take a deeper plunge in the next month than my so far erratic
look over the last 18 or more months It's working.
The above looks like it's on the right track. Is scipy some collection
of astro programs? mx is a graphics character plot?
I just hauled it into IDLE and tried executing it.
from scipy.interpolate.interpolate import interp1d
ImportError: No module named scipy.interpolate.interpolate
Apparently, something is missing.
I posted a recent msg a bit higher that will probably go unnoticed, so
I'll repeat most of it. How do I get my py code into some executable
form so that Win users who don't have python can execute it?
Both scipy and matplotlib are not part of the standard Python
distribution so they would need to be installed separately. Scipy is
useful for scientific data analysis, and matplotlib is useful for making
plots.
Since you want to wrap everything into a Windows executable, it's
probably easiest for you not to use scipy. At the least, I suspect it
would make your executable file much larger, but I've never made a
Windows executable so I don't know the details.
As for making an executable, I'm not the one to ask, but googling leads
to this:
http://effbot.org/pyfaq/how-can-i-create-a-stand-alone-binary-from-a-python-script.htm
which looks like a good place to start.
Tom
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