I have been trying to assign different colors for each line I plot, where the colors are incrementally darkened (or lightened), or selected from a colorbar (e.g. rainbow).
Any ideas?
View this message in context: incremental colors for lines
Sent from the matplotlib - users mailing list archive at Nabble.com.
(Sorry for sending this twice, Pythonified, but I forgot to copy the list)
I have been trying to assign different colors for each line I plot, where the colors are incrementally darkened (or lightened), or selected from a colorbar (e.g. rainbow).
Any ideas?
I posted some code awhile back to do what you’re looking for (see: http://old.nabble.com/Where-to-post-examples-%28specifically,-one-that-may-be-useful-for-time-evolution-plots%29-td23901837.html).
I’m copying the code below again because it’s evolved a bit (I really need to start posting code to github). Anyway, if you copy the attached code to a module, you should be able to call the “cycle_cmap” function to change the cmap globally, or the “cycle_cmap_axes” function to create an axes with the specified cmap.
Best,
-Tony
#---- start of code
import matplotlib.pyplot as plt
import numpy as np
REVERSE_CMAP = [‘summer’, ‘autumn’, ‘winter’, ‘spring’, ‘copper’]
CMAP_RANGE = dict(gray={‘start’:200, ‘stop’:0},
Blues={‘start’:60, ‘stop’:255},
Oranges={‘start’:100, ‘stop’:255},
OrRd={'start':60, 'stop':255},
BuGn={'start':60, 'stop':255},
PuRd={'start':60, 'stop':255},
YlGn={'start':60, 'stop':255},
YlGnBu={'start':60, 'stop':255},
YlOrBr={'start':60, 'stop':255},
YlOrRd={'start':60, 'stop':255},
hot={'start':230, 'stop':0},
bone={'start':200, 'stop':0},
pink={'start':160, 'stop':0})
def cmap_intervals(length=50, cmap=‘YlOrBr’, start=None, stop=None):
“”"Return evenly spaced intervals of a given colormap cmap.
Colormaps listed in REVERSE_CMAP will be cycled in reverse order. Certain
colormaps have pre-specified color ranges in CMAP_RANGE. These module
variables ensure that colors cycle from light to dark and light colors are
not too close to white.
Parameters
On Wed, May 4, 2011 at 9:51 PM, Pythonified <netdriveremail@…287…> wrote:
----------
length : int
the number of colors used before cycling back to first color. When
length is large (> ~10), it is difficult to distinguish between
successive lines because successive colors are very similar.
cmap : str
name of a matplotlib colormap (see [matplotlib.pyplot.cm](http://matplotlib.pyplot.cm/))
"""
cm = getattr([plt.cm](http://plt.cm/), cmap)
crange = CMAP_RANGE.get(cmap, dict(start=0, stop=255))
if cmap in REVERSE_CMAP:
crange = dict(start=crange['stop'], stop=crange['start'])
if start is not None:
crange['start'] = start
if stop is not None:
crange['stop'] = stop
if length > abs(crange['start'] - crange['stop']):
print ('Warning: the input length is greater than the number of ' +
'colors in the colormap; some colors will be repeated')
idx = np.linspace(crange['start'], crange['stop'], length).astype([np.int](http://np.int/))
return cm(idx)
def cycle_cmap(length=50, cmap=‘YlOrBr’, start=None, stop=None):
“”"Set default color cycle of matplotlib to a given colormap cmap.
The default color cycle of matplotlib is set to evenly distribute colors in
color cycle over specified colormap.
Note: this function must be called before *any* plot commands because it
changes the default color cycle.
See ``cmap_intervals`` for input details.
"""
color_cycle = cmap_intervals(length, cmap, start, stop)
# set_default_color_cycle doesn't play nice with numpy arrays
plt.rc('axes', color_cycle=color_cycle.tolist())
def cycle_cmap_axes(length=50, cmap=‘YlOrBr’, start=None, stop=None):
“”"Return axes with color cycle set to a given colormap cmap.
The color cycle of the axes is set to evenly distribute colors in color
cycle over specified colormap.
See ``cmap_intervals`` for input details.
"""
color_cycle = cmap_intervals(length, cmap, start, stop)
# set_default_color_cycle doesn't play nice with numpy arrays
ax = plt.gca()
ax.set_color_cycle(color_cycle)
return ax
if name == ‘main’:
n_lines = 10
x = np.linspace(0, n_lines)
# change the global cmap
cycle_cmap(n_lines, 'Oranges')
for shift in np.linspace(0, np.pi, n_lines):
plt.plot(x, np.sin(x - shift))
plt.figure()
# create an axes that is set to desired cmap
ax = cycle_cmap_axes(n_lines, 'Blues')
for shift in np.linspace(0, np.pi, n_lines):
ax.plot(x, np.sin(x - shift))
plt.show()
Pythonified wrote:
I have been trying to assign different colors for each line I plot, where
the colors are incrementally darkened (or lightened), or selected from a
colorbar (e.g. rainbow).Any ideas?
I have found a simple and better way. One can chose from colors from a color
map:
import pylab as pl
import matplotlib.cm as cm
xval = pl.arange(0, 20, 0.2)
for i in range(256):
... pl.plot(xval, pl.sin(xval)+i, c=cm.hot(i), lw=5)
This one if, for instance, picking from a color map called "hot". If one
wants to the colors to fade away, or darken, the "alpha" option can be
utilized or another color map in which colors darken or fade into another
color.
There is no need for a long sophisticated script.
Enjoy,
Pythonified
--
View this message in context: http://old.nabble.com/incremental-colors-for-lines-tp31546719p31581404.html
Sent from the matplotlib - users mailing list archive at Nabble.com.
Nice trick. This can go into the gallery or somewhere else in scipy cookbook.
On Mon, May 9, 2011 at 5:11 PM, Pythonified <netdriveremail@…287…> wrote:
Pythonified wrote:
I have been trying to assign different colors for each line I plot, where
the colors are incrementally darkened (or lightened), or selected from a
colorbar (e.g. rainbow).
Any ideas?
I have found a simple and better way. One can chose from colors from a color
map:
import pylab as pl
import matplotlib.cm as cm
xval = pl.arange(0, 20, 0.2)
for i in range(256):
... pl.plot(xval, pl.sin(xval)+i, c=cm.hot(i), lw=5)This one if, for instance, picking from a color map called “hot”. If one
wants to the colors to fade away, or darken, the “alpha” option can be
utilized or another color map in which colors darken or fade into another
color.
There is no need for a long sophisticated script.
Enjoy,
Pythonified
–
Gökhan
Hi, I like this, too.
However, I don't understand why it works at all. Usually, when I apply
a colormap, I need to take care about the scaling myself, i.e. divide
the range up into the number of elements to plot:
import pylab as pl
import matplotlib.cm as cm
xval = pl.arange(0, 20, 0.2)
n = 256
for i in range(n):
# pl.plot(xval, pl.sin(xval)+i, c=cm.hot(i), lw=5)
pl.plot(xval, pl.sin(xval)+i, c=cm.hot(1.*i/n), lw=5)
Can anyone tell me why this is not necessary here but essential for
example here:
for i,infile in enumerate(infiles):
## title for plot
tname = os.path.splitext(infile)[0]
## read data
f = FileHelpers.BlockedFile(infile)
alldata = scipy.array([,])
for ii in ['+', '2', 'x', '1']: # use for markers, too
# for ii in [4,3,2,1]: # use for markers, too
try:
f.next_block()
data = scipy.loadtxt(f).T
alldata = scipy.concatenate((alldata, data), axis=1)
# ax.plot(data[0],data[1], '%s'%ii,
color=cm.hot(1.*i/len(infiles)), mew=1.5 )
ax.plot(data[0],data[1], '%s'%ii, c=cm.hot(i), mew=1.5 )
except Exception, e:
print e
break
Thanks in advance,
Daniel
I have found a simple and better way. One can chose from colors from a
color
map:>>import pylab as pl
>>import matplotlib.cm as cm
>>xval = pl.arange(0, 20, 0.2)
>>for i in range(256):
... pl.plot(xval, pl.sin(xval)+i, c=cm.hot(i), lw=5)This one if, for instance, picking from a color map called "hot". If one
wants to the colors to fade away, or darken, the "alpha" option can be
utilized or another color map in which colors darken or fade into another
color.There is no need for a long sophisticated script.