Hi Jason, Hi list, First of all let me say I like the EngFormatter of Jason. Are there plans to incorparate it into matplotlib? I cannot find any indication for this in current svn, but I would like to see the EngFormatter in matplotlib. Therefore I tried to include Jasons proposal into the ticker.py as a new class EngFormatter including the method 'self.format_eng'. I made some changes, which might break some of Jasons ideas, but I cannot see (1) why we need the LogFormatter as base class instead of Formatter? (2) why one should decide for only decade-labels. Therefore I removed the corresponding if-statement. It causes errors () if you use an axes including '0', which could be useful for eng-formatting, too. (3) Could we always use format_str = "%g %s" instead of specifying 'places'? Because of successive zomming I don't want to specify 'places' before calling 'plt.show'. Therefore I introduced "places =None" to use "%g %s".
I attached the new ticker.py and a diff against current svn (I'm sorry I couldn't resist to add some white spaces). Any comments are welcome. Kind regards, Matthias Michler On Wednesday 25 November 2009 01:39:43 Jason Heeris wrote: > Hi, > > 2009/11/18 Jason Heeris <jason.hee...@gmail.com>: > > In gnuplot, I can do the following: > > > > set format x "%.0s %cHz" > > > > ...and this will set the x-axis labels (on a semilogx style plot) to > > be "10 Hz", "100 Hz", "1 kHz", "10 kHz", etc. > > I ended up implementing this myself, it wasn't too hard. I've attached > the code if anyone else is interested. I don't know matplotlib that > well, so I don't know if there's much duplication of code in there. > > I thought I'd CC the dev list in case others think it might be useful. > If not, sorry for the noise. > > Cheers, > Jason
Index: ticker.py
===================================================================
--- ticker.py (revision 8000)
+++ ticker.py (working copy)
@@ -118,6 +118,7 @@
from __future__ import division
+import decimal
import math
import numpy as np
from matplotlib import rcParams
@@ -507,23 +508,23 @@
is ``False``
"""
self._base = base+0.0
- self.labelOnlyBase=labelOnlyBase
+ self.labelOnlyBase = labelOnlyBase
self.decadeOnly = True
- def base(self,base):
+ def base(self, base):
'change the *base* for labeling - warning: should always match the base used for :class:`LogLocator`'
- self._base=base
+ self._base = base
- def label_minor(self,labelOnlyBase):
+ def label_minor(self, labelOnlyBase):
'switch on/off minor ticks labeling'
- self.labelOnlyBase=labelOnlyBase
+ self.labelOnlyBase = labelOnlyBase
def __call__(self, x, pos=None):
'Return the format for tick val *x* at position *pos*'
vmin, vmax = self.axis.get_view_interval()
d = abs(vmax - vmin)
- b=self._base
+ b = self._base
if x == 0.0:
return '0'
sign = np.sign(x)
@@ -533,13 +534,13 @@
if not isDecade and self.labelOnlyBase: s = ''
elif x>10000: s= '%1.0e'%x
elif x<1: s = '%1.0e'%x
- else : s = self.pprint_val(x,d)
+ else : s = self.pprint_val(x, d)
if sign == -1:
s = '-%s' % s
return self.fix_minus(s)
- def format_data(self,value):
+ def format_data(self, value):
self.labelOnlyBase = False
value = cbook.strip_math(self.__call__(value))
self.labelOnlyBase = True
@@ -554,14 +555,14 @@
return abs(x-n)<1e-10
def nearest_long(self, x):
- if x==0: return 0L
- elif x>0: return long(x+0.5)
+ if x == 0: return 0L
+ elif x > 0: return long(x+0.5)
else: return long(x-0.5)
def pprint_val(self, x, d):
#if the number is not too big and it's an int, format it as an
#int
- if abs(x)<1e4 and x==int(x): return '%d' % x
+ if abs(x) < 1e4 and x == int(x): return '%d' % x
if d < 1e-2: fmt = '%1.3e'
elif d < 1e-1: fmt = '%1.3f'
@@ -572,7 +573,7 @@
s = fmt % x
#print d, x, fmt, s
tup = s.split('e')
- if len(tup)==2:
+ if len(tup) == 2:
mantissa = tup[0].rstrip('0').rstrip('.')
sign = tup[1][0].replace('+', '')
exponent = tup[1][1:].lstrip('0')
@@ -645,11 +646,106 @@
if usetex:
s = r'$%s%d^{%d}$'% (sign_string, b, self.nearest_long(fx))
else:
- s = r'$\mathdefault{%s%d^{%d}}$'% (sign_string, b, self.nearest_long(fx))
+ s = r'$\mathdefault{%s%d^{%d}}$'% (sign_string, b,
+ self.nearest_long(fx))
return s
+class EngFormatter(Formatter):
+ """
+ Formats axis values using engineering prefixes to represent powers of 1000,
+ plus a specified unit, eg. 10 MHz instead of 1e7.
+ example:
+ from matplotlib.ticker import EngFormatter
+ formatter = EngFormatter(unit='Hz')
+ ax = plt.subplot(111)
+ ax.xaxis.set_major_formatter(formatter)
+ ax.plot(np.arange(100), np.random.uniform(size=100))
+
+ """
+ # The SI engineering prefixes
+ ENG_PREFIXES = {
+ -24: "y",
+ -21: "z",
+ -18: "a",
+ -15: "f",
+ -12: "p",
+ -9: "n",
+ -6: u"\u03bc", # Greek letter mu
+ -3: "m",
+ 0: "",
+ 3: "k",
+ 6: "M",
+ 9: "G",
+ 12: "T",
+ 15: "P",
+ 18: "E",
+ 21: "Z",
+ 24: "Y"
+ }
+
+ def __init__(self, unit="", places=None):
+ self.unit = unit
+ self.places = places
+
+ def __call__(self, x, pos=None):
+
+ s = "%s%s" % (self.format_eng(x), self.unit)
+
+ return self.fix_minus(s)
+
+ def format_eng(self, num):
+ """ Formats a number in engineering notation, appending a letter
+ representing the power of 1000 of the original number. Some examples:
+
+ >>> format_eng(0) for self.places = 0
+ '0'
+
+ >>> format_eng(1000000) for self.places = 1
+ '1.0 M'
+
+ >>> format_eng("-1e-6") for self.places = 2
+ u'-1.00 \u03bc'
+
+ @param num: the value to represent
+ @type num: either a numeric value or a string that can be converted to a
+ numeric value (as per decimal.Decimal constructor)
+
+ @return: engineering formatted string
+ """
+
+ dnum = decimal.Decimal(str(num))
+
+ sign = 1
+
+ if dnum < 0:
+ sign = -1
+ dnum = -dnum
+
+ if dnum != 0:
+ pow10 = decimal.Decimal(int(math.floor(dnum.log10()/3)*3))
+ else:
+ pow10 = decimal.Decimal(0)
+
+ pow10 = pow10.min(max(self.ENG_PREFIXES.keys()))
+ pow10 = pow10.max(min(self.ENG_PREFIXES.keys()))
+
+ prefix = self.ENG_PREFIXES[int(pow10)]
+
+ mant = sign*dnum/(10**pow10)
+
+ if self.places is None:
+ format_str = u"%g %s"
+ elif self.places == 0:
+ format_str = u"%i %s"
+ elif self.places > 0:
+ format_str = (u"%%.%if %%s" % places)
+
+ formatted = format_str % (mant, prefix)
+
+ return formatted.strip()
+
class Locator(TickHelper):
"""
Determine the tick locations;
ticker.py
Description: application/python
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