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291 lines
9.5 KiB
Python
291 lines
9.5 KiB
Python
#
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# Copyright (c) 2009 Tom Keffer <tkeffer@gmail.com>
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#
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# See the file LICENSE.txt for your full rights.
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#
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# Revision: $Rev$
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# Author: $Author$
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# Date: $Date$
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#
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"""Various utilities used by the plot package.
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"""
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import datetime
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import time
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import math
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import weeplot
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def scale(fmn, fmx, prescale = None):
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"""Calculates an appropriate min, max, and step size for scaling axes on a plot.
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Reference: 2003 Pharmasug 2003 by Don Li "Tired of Defining Axis Scale for
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SAAS Graphs? A Solution with Automatic Optimizing Approach."
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http://www.lexjansen.com/pharmasug/2003/coderscorner/cc024.pdf
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fmn: The minimum data value
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fmx: The maximum data value. Must be greater than or equal to fmn.
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prescale: One or more of the results may be preset. [optional]
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Returns: a three-way tuple. First value is the lowest scale value, second the highest.
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The third value is the step (increment) between them.
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"""
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minscale = maxscale = interval = None
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if prescale is not None :
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minscale = prescale[0]
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maxscale = prescale[1]
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interval= prescale[2]
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if fmx < fmn :
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raise weeplot.ViolatedPrecondition, "scale() called with max value less than min value"
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if minscale is not None :
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fmn = minscale
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if maxscale is not None :
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fmx = maxscale
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if fmx == fmn :
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if fmn == 0.0 :
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fmx = 1.0
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else :
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fmx = fmn + .01*abs(fmn)
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amin = math.floor(fmn)
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amax = math.ceil(fmx)
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range = amax-amin
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unit = range/10.0
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grade = math.floor(math.log10(unit))
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sunit = unit / math.pow(10.0, grade)
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if interval is None :
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if sunit < math.sqrt(2.0) :
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interval = math.pow(10.0, grade)
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elif sunit < math.sqrt(10.0) :
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interval = math.pow(10.0, grade) * 2.0
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elif sunit < math.sqrt(50.0) :
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interval = math.pow(10.0, grade) * 5.0
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else :
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interval = pow(10.0, grade+1)
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if maxscale is None :
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maxscale = math.ceil(amax/interval) * interval
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if minscale is None :
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minscale = math.floor(amin/interval) * interval
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return (minscale, maxscale, interval)
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def scaletime(tmin_ts, tmax_ts) :
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"""Picks a time scaling suitable for a time plot.
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tmin_ts, tmax_ts: The time stamps in epoch time around which the times will be picked.
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Returns a scaling 3-tuple. First element is the start time, second the stop
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time, third the increment. All are in seconds (epoch time in the case of the
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first two).
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"""
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if tmax_ts <= tmin_ts :
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raise weeplot.ViolatedPrecondition, "scaletime called with tmax <= tmin"
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tdelta = tmax_ts - tmin_ts
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tmin_dt = datetime.datetime.fromtimestamp(tmin_ts)
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tmax_dt = datetime.datetime.fromtimestamp(tmax_ts)
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# How big a time delta are we talking about?
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if tdelta <= 27 * 3600 :
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# A day plot is wanted. A time increment of 3 hours is appropriate
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# h is the hour of tmin_dt
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h = tmin_dt.timetuple()[3]
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# Subtract off enough to get to the lower 3-hour boundary,
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# zeroing out everything else
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start_dt = tmin_dt.replace(minute=0, second=0, microsecond=0) - datetime.timedelta(hours = h % 3)
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# Now figure the upper time boundary, which is a bit more complicated if tmax_dt lies
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# near the 3-hour boundary
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tmax_tt = tmax_dt.timetuple()
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# stop_dt is the lower 3-hour boundary from tmax_dt
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stop_dt = tmax_dt.replace(minute=0, second=0, microsecond=0)
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# If the tmax_dt was close to the 3-hour boundary, we're done. Otherwise, go up to
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# the next 3-hour boundary.
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if tmax_tt[3] % 3 != 0 or tmax_tt[4] != 0 :
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stop_dt += datetime.timedelta(hours = 3 - tmax_tt[3] % 3)
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interval = 3 * 3600
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elif tdelta > 27 * 3600 and tdelta <= 31 * 24 * 3600 :
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# The time scale is between a day and a month. A time increment of one day is appropriate
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start_dt = tmin_dt.replace(hour=0, minute=0, second=0, microsecond=0)
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stop_dt = tmax_dt.replace(hour=0, minute=0, second=0, microsecond=0)
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tmax_tt = tmax_dt.timetuple()
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if tmax_tt[3]!=0 or tmax_tt[4]!=0 :
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stop_dt += datetime.timedelta(days=1)
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interval = 24 * 3600
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else :
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# The time scale is more than a month. A time increment of a month is appropriate
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start_dt = tmin_dt.replace(day=1, hour=0, minute=0, second=0, microsecond=0)
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(year , mon, day) = tmax_dt.timetuple()[0:3]
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if day != 1 :
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mon += 1
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if mon==13 :
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mon = 1
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year += 1
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stop_dt = datetime.datetime(year, mon, 1)
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# Average month length:
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interval = 365.25/12 * 24 * 3600
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# Convert to epoch time stamps
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start_ts = time.mktime(start_dt.timetuple())
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stop_ts = time.mktime(stop_dt.timetuple())
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return (start_ts, stop_ts, interval)
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class ScaledDraw(object):
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"""Like an ImageDraw object, but lines are scaled.
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"""
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def __init__(self, draw, imagebox, scaledbox):
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"""Initialize a ScaledDraw object.
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Example:
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scaledraw = ScaledDraw(draw, ((10, 10), (118, 246)), ((0.0, 0.0), (10.0, 1.0)))
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would create a scaled drawing where the upper-left image coordinate (10, 10) would
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correspond to the scaled coordinate( 0.0, 1.0). The lower-left image coordinate
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would correspond to the scaled coordinate (10.0, 0.0).
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draw: an instance of ImageDraw
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imagebox: a 2-tuple of the box coordinates on the image ((ulx, uly), (lrx, lry))
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scaledbox: a 2-tuple of the box coordinates of the scaled plot ((llx, lly), (urx, ury))
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"""
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uli = imagebox[0]
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lri = imagebox[1]
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lls = scaledbox[0]
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urs = scaledbox[1]
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self.xscale = (lri[0] - uli[0]) / (urs[0] - lls[0])
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self.yscale = -(lri[1] - uli[1]) / (urs[1] - lls[1])
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self.xoffset = lri[0] - urs[0] * self.xscale
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self.yoffset = uli[1] - urs[1] * self.yscale
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self.draw = draw
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def line(self, x, y, **options) :
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"""Draw a scaled line on the instance's ImageDraw object.
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x: sequence of x coordinates
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y: sequence of y coordinates, some of which are possibly null (value of None)
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"""
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# Break the line up around any nulls
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for (x_seq, y_seq) in seq_line(x, y):
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# Scale it
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xy_seq_scaled = zip([self.xtranslate(x) for x in x_seq],
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[self.ytranslate(y) for y in y_seq])
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# Draw it:
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if len(xy_seq_scaled) == 1 :
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self.draw.point(xy_seq_scaled, fill = options['fill'])
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else :
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self.draw.line(xy_seq_scaled, **options)
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def rectangle(self, box, **options) :
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"""Draw a scaled rectangle.
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box: A pair of 2-way tuples, containing coordinates of opposing corners
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of the box.
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options: passed on to draw.rectangle. Usually contains 'fill' (the color)
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"""
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box_scaled = [(coord[0]*self.xscale + self.xoffset + 0.5, coord[1]*self.yscale + self.yoffset + 0.5) for coord in box]
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self.draw.rectangle(box_scaled, **options)
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def xtranslate(self, x):
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return int(x * self.xscale + self.xoffset + 0.5)
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def ytranslate(self, y):
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return int(y * self.yscale + self.yoffset + 0.5)
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def seq_line(x, y):
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"""Generator function that breaks a line up into individual segments around any nulls held in y.
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Example: if x=[0, 1, 2, 3, 4, 5, 6, 7]
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y=[10, 20, None, 40, None, 60, 70, None]
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then
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seq_line(x,y) yields
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([0,1], [10,20])
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([3], [40])
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([5,6], [60,70])
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x: iterable sequence of x coordinates. All values must be non-null
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y: iterable sequence of y coordinates, possibly with some embedded
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nulls (that is, their value==None)
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yields: tuples, first value of which is a list of x-coordinates, and second value a list of y-coordinates,
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of a contiguous line
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"""
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istart = iend = 0
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while iend < len(y):
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if y[iend] is None:
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if istart != iend :
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yield (x[istart:iend], y[istart:iend])
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istart = iend + 1
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while istart < len(y) :
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if y[istart] is not None :
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break
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istart += 1
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iend = istart
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iend += 1
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if istart < len(y) :
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yield (x[istart:iend], y[istart:iend])
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def pickLabelFormat(increment):
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i_log = math.log10(increment)
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if i_log < 0 :
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i_log = abs(i_log)
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decimal_places = int(i_log)
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if i_log != decimal_places :
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decimal_places += 1
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else :
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decimal_places = 0
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return "%%.%df" % decimal_places
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if __name__ == '__main__' :
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import time
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# Unit test:
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assert(scale(1.1, 12.3) == (1.0, 13.0, 1.0))
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assert(scale(-1.1, 12.3) == (-2.0, 14.0, 2.0))
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assert(scale(-12.1, -5.3) == (-13.0, -5.0, 1.0))
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t= time.time()
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scaletime(t - 24*3600 - 20, t)
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assert(pickLabelFormat(1) == "%.0f")
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assert(pickLabelFormat(20) == "%.0f")
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assert(pickLabelFormat(.2) == "%.1f")
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assert(pickLabelFormat(.1) == "%.1f")
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print "test successful"
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