/usr/lib/python2.7/dist-packages/chaco/scales/time_scale.py is in python-chaco 4.5.0-1.
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A scale for time and calendar intervals.
"""
from math import floor
from scales import AbstractScale, ScaleSystem, frange, heckbert_interval
from formatters import TimeFormatter
from safetime import (safe_fromtimestamp, datetime, timedelta, EPOCH,
MINYEAR, MAXYEAR)
# Labels for date and time units.
datetime_scale = ["microsecond", "second", "minute", "hour",
"day", "month", "year"]
datetime_zeros = zip(datetime_scale, [0, 0, 0, 0, 1, 1, 1])
__all__ = ["TimeScale", "CalendarScaleSystem", "HMSScales", "MDYScales",
"trange", "tfrac", "td_to_sec", "dt_to_sec"]
def td_to_sec(td):
""" Returns the floating point number of seconds in a timedelta object.
"""
return td.days * 24 * 3600 + td.seconds + td.microseconds * 1e-6
def dt_to_sec(t):
""" Returns the floating point number of seconds since the UNIX epoch
corresponding to the given datetime instance.
This value is more accurate than mktime(t.timetuple()) because it
preserves milliseconds.
"""
return td_to_sec(t - EPOCH)
def tfrac(t, **time_unit):
""" Performs a calendar-aware split of a time into (aligned_time, frac)
over an interval that is a multiple of one of the following time units:
"microseconds" "milliseconds", "seconds", "minutes", "hours", "days", "years"
Settings of milliseconds..hours are truncated towards 0, days are counted
from January 1st of their respective year, and years are counted from 1 AD.
This may lead to unexpected rounding if multi-day or multi-year intervals
are used.
For example:
If it is currently 4:15pm on January 3rd, 2007, calling:
``tfrac(time.time(), hours=3)``
returns the UNIX number of seconds corresponding to
"January 3rd, 2007 15:00:00"
as the aligned time, and the number of seconds in 1 hour and 15 minutes as
the fractional part.
Parameters
==========
t : float
time in seconds
``**time_unit`` : dict
a single (interval=value) item
Returns
=======
A tuple: (aligned time as UNIX time, remainder in seconds)
"""
unit, period = time_unit.items()[0]
if unit == "milliseconds":
unit = "microsecond"
period *= 1000
else:
unit = unit[:-1] # strip off the 's'
# Find the nearest round date
dt = safe_fromtimestamp(t)
amt = getattr(dt, unit)
ndx = datetime_scale.index(unit)
closest_multiple = int(floor(amt / period) * period)
if closest_multiple == 0 and unit in ("day", "year"):
# TODO: this isn't really quite right for intervals of days > 1...
closest_multiple = 1
whole = dt.replace(**{unit: closest_multiple})
whole = whole.replace(**dict(datetime_zeros[:ndx]))
frac = td_to_sec(dt - whole)
return dt_to_sec(whole), frac
def _advance_month(dt, months):
""" Advance a datetime object by a given number of months.
"""
new_month = dt.month + months
years, extra_months = divmod(new_month-1, 12)
new_month = extra_months + 1
return dt.replace(year=dt.year+years, month=new_month)
def trange_months(start, end, months):
""" Create a range of timestamps separated by a given number of months.
The start of the iteration is always aligned to Jan 1 2000.
"""
dt_start = safe_fromtimestamp(start)
dt_end = safe_fromtimestamp(end)
dmonths = (12 * (dt_start.year - 2000) + dt_start.month - 1) % months
dt = _advance_month(dt_start.replace(day=1, hour=0, minute=0, second=0,
microsecond=0), -dmonths)
while dt < dt_start:
dt = _advance_month(dt, months)
timestamps = []
while dt <= dt_end:
timestamps.append(dt_to_sec(dt))
dt = _advance_month(dt, months)
return timestamps
def _advance_years(dt, years):
""" Advance a datetime object by a given number of years.
"""
return dt.replace(year=dt.year+years)
def trange_years(start, end, years):
""" Create a range of timestamps separated by a given number of years.
The start of the iteration is aligned to Jan 1 2000.
"""
dt_start = safe_fromtimestamp(start)
dt_end = safe_fromtimestamp(end)
dyears = (dt_start.year - 2000) % years
if dyears < 0:
dyears += years
dt = datetime(dt_start.year-dyears, 1, 1, 0, 0, 0, 0)
while dt < dt_start:
dt = _advance_years(dt, years)
timestamps = []
while dt <= dt_end:
timestamps.append(dt_to_sec(dt))
dt = _advance_years(dt, years)
return timestamps
def trange(start, end, **time_unit):
""" Like range(), but for times, and with "natural" alignment depending on
the interval.
For example::
t_range(time.time(), time.time()+76*3600, days=2)
t_range(start, end, months=3)
Parameters
==========
start, end : float
Time in seconds. *end* must be later than *start*.
time_unit : a single (key, int_value) pair
The units to use. *key* must be in the list: "milliseconds", "seconds",
"minutes", "hours", "days", "months", "years". Months are treated as
30 days, and years are treated as 365 days.
Returns
=======
A list of times that nicely span the interval, or an empty list if *start*
and *end* fall within the same interval.
"""
if len(time_unit) > 1:
raise ValueError("trange() only takes one keyword argument, got %d" % len(time_unit))
# Months and years are non-uniform, so we special-case them.
unit, value = time_unit.items()[0]
if unit == 'months':
return trange_months(start, end, value)
elif unit == 'years':
return trange_years(start, end, value)
# Express start and end ticks as (date, frac) where date is calendar-aligned
# with the interval in time_unit.
start_whole, start_frac = tfrac(start, **time_unit)
end_whole, end_frac = tfrac(end, **time_unit)
# Handle some corner-cases
if start_whole == end_whole:
return []
if start_frac < 1e-6:
first_tick_ndx = 0
else:
first_tick_ndx = 1
# Convert months and years into days
time_unit["days"] = time_unit.setdefault("days", 0) + \
365 * time_unit.pop("years", 0) + \
30 * time_unit.pop("months", 0)
delta = td_to_sec(timedelta(**time_unit))
count = (end_whole - start_whole) / delta
ticks = [start_whole + i*delta for i in range(int(round(count))+1)]
return ticks[first_tick_ndx:]
class TimeScale(AbstractScale):
""" A scale based on time intervals and calendar dates. The valid
intervals are:
Natural time:
microseconds, milliseconds, seconds, minutes, hours, days, years
Calendar time:
day_of_month, month_of_year
For calendar times, a list of hours/days/months is set.
By default, intervals are aligned to January 1st.
"""
# This is used to compute an approximate resolution for each type of scale.
SECS_PER_UNIT = {"microseconds": 1e-6,
"milliseconds": 1e-3,
"seconds": 1,
"minutes": 60,
"hours": 3600,
"days": 24*3600,
"day_of_month": 30*24*3600,
"month_of_year": 365*24*3600,
"years": 365*24*3600,
}
CALENDAR_UNITS = ("day_of_month", "month_of_year")
def __init__(self, **kw_interval):
""" Defines the time period that this scale uses.
"""
self.formatter = kw_interval.pop("formatter", TimeFormatter())
unit, val = kw_interval.items()[0]
self.unit = unit
if "_of_" in unit:
# Calendar time interval - divide by the number of ticks per larger
# unit of time to get an average resolution
if type(val) in (int, float):
val = [val]
self.vals = val
self.resolution = self.SECS_PER_UNIT[unit] / float(len(val))
else:
self.val = val
self.resolution = val * self.SECS_PER_UNIT[unit]
return
def num_ticks(self, start, end, desired_ticks=None):
""" Returns an approximate number of ticks that this scale
produces for the given interval.
Implements AbstractScale.
"""
# This is only approximate, but puts us in the ballpark
if self.unit in ("milliseconds", "microseconds"):
ticks = self.ticks(start, end, desired_ticks=8)
coarsest_scale_count = (end - start) / (500 * self.SECS_PER_UNIT[self.unit])
return max(len(ticks), coarsest_scale_count)
else:
return (end - start) / self.resolution
def ticks(self, start, end, desired_ticks=None):
""" Returns the set of "nice" positions on this scale that enclose and
fall inside the interval (*start*,*end*).
Implements AbstractScale. The *start* and *end* parameters are
floating-point seconds since the epoch.
"""
if self.unit in self.CALENDAR_UNITS:
return self.cal_ticks(start, end)
elif self.unit in ("milliseconds", "microseconds"):
if start == end or (end - start) < self.SECS_PER_UNIT[self.unit]:
return [start]
secs_per_unit = self.SECS_PER_UNIT[self.unit]
start /= secs_per_unit
end /= secs_per_unit
if desired_ticks is None:
min, max, delta = heckbert_interval(start, end, enclose=True)
else:
min, max, delta = heckbert_interval(start, end, desired_ticks,
enclose=True)
min *= secs_per_unit
max *= secs_per_unit
delta *= secs_per_unit
return frange(min, max, delta)
else:
return trange(start, end, **{self.unit: self.val})
def cal_ticks(self, start, end):
""" ticks() method for calendar-based intervals """
try:
start = datetime.fromtimestamp(start)
except ValueError:
start = datetime(MINYEAR, 1, 1, 0, 0, 0)
try:
end = datetime.fromtimestamp(end)
except ValueError:
end = datetime(MAXYEAR, 1, 1, 0, 0, 0)
if self.unit == "day_of_month":
s = start.year + 1/12.0 * start.month
e = end.year + 1/12.0 * end.month
num_months = int(round((e - s) * 12)) + 1 # add 1 for fencepost
start_year = start.year
start_month = start.month
ym = [divmod(i, 12)
for i in range(start_month-1, start_month-1+num_months)]
months = [start.replace(year=start_year+y, month=m+1, day=1)
for (y,m) in ym]
ticks = [dt.replace(day=i) for dt in months for i in self.vals]
elif self.unit == "month_of_year":
years = [start.replace(year=newyear, day=1)
for newyear in range(start.year, end.year+1)]
ticks = [dt.replace(month=i, day=1)
for dt in years for i in self.vals]
else:
raise ValueError("Unknown calendar unit '%s'" % self.unit)
if len(ticks) > 0:
# Find the first and last index in all_ticks that falls
# within (start,end)
for start_ndx in range(len(ticks)):
if ticks[start_ndx] >= start:
break
for end_ndx in range(len(ticks)-1, 0, -1):
if ticks[end_ndx] <= end:
break
ticks = ticks[start_ndx : end_ndx+1]
return map(dt_to_sec, ticks)
def labels(self, start, end, numlabels=None, char_width=None):
""" Returns a series of ticks and corresponding strings for labels
that fall inside the interval (*start*,*end*).
Overrides AbstractScale.
"""
ticks = self.ticks(start, end, numlabels)
labels = self.formatter.format(ticks, numlabels, char_width, ticker=self)
return zip(ticks, labels)
def label_width(self, start, end, numlabels=None, char_width=None):
""" Returns an estimate of total number of characters used by the
the labels that this scale will produce for the given set of
inputs, as well as the number of labels.
Overrides AbstractScale.
"""
return self.formatter.estimate_width(start, end, numlabels, char_width,
ticker=self)
# Declare some default scale systems
# Default time scale for hours, minutes, seconds, and milliseconds.
HMSScales = [TimeScale(microseconds=1), TimeScale(milliseconds=1)] + \
[TimeScale(seconds=dt) for dt in (1, 5, 15, 30)] + \
[TimeScale(minutes=dt) for dt in (1, 5, 15, 30)] + \
[TimeScale(hours=dt) for dt in (1, 2, 3, 4, 6, 12, 24)]
# Default time scale for months, days, and years.
MDYScales = [TimeScale(day_of_month=range(1,31,3)),
TimeScale(day_of_month=(1,8,15,22)),
TimeScale(day_of_month=(1,15)),
TimeScale(month_of_year=range(1,13)),
TimeScale(month_of_year=range(1,13,3)),
TimeScale(month_of_year=(1,7)),
TimeScale(month_of_year=(1,)),] + \
[TimeScale(years=dt) for dt in (1,2,5,10)]
class CalendarScaleSystem(ScaleSystem):
""" Scale system for calendars.
This class has a pre-defined set of nice "time points" to use for ticking
and labelling.
"""
def __init__(self, *scales, **kw):
""" Creates a new CalendarScaleSystem.
If scales are not provided, then it defaults to HMSScales and MDYScales.
"""
if len(scales) == 0:
scales = HMSScales + MDYScales
super(CalendarScaleSystem, self).__init__(*scales, **kw)
def _get_scale(self, start, end, numticks):
if len(self.scales) == 0:
if self.default_scale is not None:
closest_scale = self.default_scale
else:
raise ValueError("CalendarScaleSystem has not be configured "
"with any scales.")
elif end - start < 1e-6 or end - start > 1e5 * 365 * 24 * 3600:
closest_scale = self.default_scale
else:
closest_scale = self._get_scale_np(start, end, numticks)
return closest_scale
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