Plotting time vs date in R

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Having done the plot with python+matplotlib, thought I would have a go reproducing it in R, using only the builtin “plot”. So, just to recap – this is a plot of the sun times (rise/set,twilight and blinding) as generated by the great python library pyephem. The R code reads in a csv file as output from a modified version of the python code used in my original post.

For completeness, the csv generation code is below:

import ephem
import datetime, math
import pylab
 
place = ephem.city('Melbourne')
 
start_date = datetime.datetime(2009,12,1,12)
end_date = datetime.datetime(2011, 1, 31,12)
 
base_offset = '0'
twilight_offset = '-6:00:0.0' # "twilight" = centre of the sun is -6deg ideal horizon
eyeline_offset = '15:34:0.0' # arbitrary +15deg
 
sun = ephem.Sun(place)
 
dates = []
sunrise = []
sunset = []
firstlight = []
lastlight = []
firsteyel = []
lasteyel = []

numdays = (end_date - start_date).days
dates = [start_date + datetime.timedelta(days=i) for i in xrange(numdays+1)] 
dates.sort()

def dt2m(dt):
    return (dt.hour*60) + dt.minute

def m2hm(x):
    h = int(x/60)
    m = int(x%60)
    return '%(h)02d%(m)02d' % {'h':h,'m':m}

sunrise = map(lambda x:dt2m(ephem.localtime(place.next_rising(sun,start=x))),dates)
sunset = map(lambda x:dt2m(ephem.localtime(place.next_setting(sun,start=x))),dates)

place.horizon = twilight_offset
firstlight = map(lambda x:dt2m(ephem.localtime(place.next_rising(sun,start=x))),dates)
lastlight = map(lambda x:dt2m(ephem.localtime(place.next_setting(sun,start=x))),dates)

place.horizon = eyeline_offset
firsteyel = map(lambda x:dt2m(ephem.localtime(place.next_rising(sun,start=x))),dates)
lasteyel = map(lambda x:dt2m(ephem.localtime(place.next_setting(sun,start=x))),dates)

writer = open("suntimes.csv", "w")
writer.write("date,firstlight,sunrise,firsteyel,lasteyel,sunset,lastlight\n")
for n in xrange(numdays):
 writer.write(str(dates[n]) +","+  (m2hm(firstlight[n]))+"," \
 + m2hm(sunrise[n])+"," + m2hm(firsteyel[n])+"," + m2hm(lasteyel[n])+"," \
 + m2hm(sunset[n])+"," + m2hm(lastlight[n])+"\n")
writer.close()
 
 

I chose to leave the format of the times, as they resemble the format of the Geoscience Australia times.

This is how the csv file looks:

date,firstlight,sunrise,firsteyel,lasteyel,sunset,lastlight
2009-12-01 00:00:00,0518,0551,0719,1858,2026,2059
2009-12-02 00:00:00,0518,0551,0719,1859,2027,2100
2009-12-03 00:00:00,0518,0551,0719,1859,2028,2101
2009-12-04 00:00:00,0518,0551,0719,1900,2029,2102
2009-12-05 00:00:00,0518,0550,0719,1901,2030,2103

And here’s the resulting graph:

Here’s the R code:

suntimes 

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