2010/10/18 Friedrich Romstedt <friedrichromst...@gmail.com>:
> 2010/10/18 脑关(BrainGateway)生命科学仪器 <braingate...@gmail.com>:
>> On Mon, Oct 18, 2010 at 12:54 AM, Benjamin Root <ben.r...@ou.edu> wrote:
>>> On Sun, Oct 17, 2010 at 5:35 PM, braingateway <braingate...@gmail.com>
>>> wrote:
>>>> I tried all possible colormaps and found out: gist_rainbow, terrain,
>>>> bwr, brg, and seismic will generate the same error, all other colormaps
>>>> are OK. I wonder is this a bug or expected behavior?
>> Hi Ben,
>> Thanks a lot for answering my question! I am a newbie to matplotlib,
>> so please forgive me, if the question is stupid ;p
>
> Questions are never stupid ...
>
>> In my program I wanna know the exact RGBA value of a data point in the
>> figure, in order to plot a corresponding line with the same color in
>> another figure. That is why I need to call a(z) to get RGBA value of a
>> point at (x,y,z) (z is represented by color). If I understood it
>> correctly, you said I do not need to specify the 'lut' in
>> cm.get_cmap(name,lut)? I thought the colormap object is actually a
>> lookup table with a length specified by lut.
>
> Kind of, but it's initialised from a linear segmentation dictionary,
> so you can get cmaps with a precision you want.
>
>> It turns out I do not
>> need to specify anything here.
>
> Default param is 256.
>
>> But if I do not specify anything the
>> colormap.N is always 256. What will happen then, if I need more color
>> steps?
>
> cm = get_cmap('...', 1024)
>
>> I do notice a(2) and a(2.2) returns different values. So I am
>> very confused about the principle how the RGBA value is generated by
>> the colormaps.
>
> It's the "magic" to distinguish between integer (in the LUT range) and
> float (in [0.0, 1.0]). 2 gives the LUT entry 2, 2.0 will give the
> upper value since it's > 1, as will 2.2 do. Try 0.5, and 0.6, or 0.0
> and 0.1.
>
> Actually I cannot reproduce your error on a recently (some weeks ago)
> checked-out GitHub repo version of mpl 1.0.0. Please provide
> mpl.__version__ so that we check if that's the reason - as simple as
> it might be.
>
> MacBook-Pro-Friedrich:Report Friedrich$ python
> Python 2.6.5 (r265:79063, Jul 18 2010, 12:14:53)
> [GCC 4.2.1 (Apple Inc. build 5659)] on darwin
> Type "help", "copyright", "credits" or "license" for more information.
>>>> import matplotlib.cm
>>>> cm = matplotlib.cm.get_cmap('gist_rainbow')
>>>> cm(range(256))
> array([[ 1. , 0. , 0.16 , 1. ],
> [ 1. , 0. , 0.13908497, 1. ],
> [ 1. , 0. , 0.11816993, 1. ],
> ...,
> [ 1. , 0. , 0.79262575, 1. ],
> [ 1. , 0. , 0.77131287, 1. ],
> [ 1. , 0. , 0.75 , 1. ]])
>>>> print matplotlib.__version__
> 1.0.0
>
> The attribute of the cm where the error occurs on your machine is set
> to a valid value for me. I also cannot find any code path leading to
> a wrong initialisation of the attribute. Might be that the data the
> cm is init'ed from changed. There is a code path initialising the cm
> from a tuple (your attribute was a tuple used like a dict), but this
> works too: (terrain is such an example):
>
>>>> cm = matplotlib.cm.get_cmap('terrain')
>>>> cm(range(256))
> array([[ 0.2 , 0.2 , 0.6 , 1. ],
> [ 0.19477124, 0.21045752, 0.61045752, 1. ],
> [ 0.18954248, 0.22091503, 0.62091503, 1. ],
> ...,
> [ 0.98431373, 0.97992157, 0.97898039, 1. ],
> [ 0.99215686, 0.98996078, 0.9894902 , 1. ],
> [ 1. , 1. , 1. , 1. ]])
>
> Might be that there was 'red' misspelled in gist_rainbow in you mpl
> version, this may explain the behaviour if we track it down. Can you
> do the following to verify this:
>
> import matplotlib._cm
> print matplotlib._cm._gist_stern_data
>
> ? Thx,
> Friedrich
>
Thanks a lot for your detailed response!
In previous posts I did give the version: '1.0.svn'. Then I installed
the latest stable version. Here is the version info:
>>> print matplotlib.__version__
1.0.0
However, the error is still there.
You could not reproduce the error in your code, because you did not
specify 'lut' when you call get_cmap
try this:
maps=[m for m in matplotlib.cm.datad if not m.endswith("_r")]
for i in maps:
try:
a=matplotlib.cm.get_cmap(i,256)(range(256))
except:
(type, value, traceback) = sys.exc_info()
print "Problems to create %s" % (i,)
print "The error was --> %s: %s" % (type, value)
u will reproduce the error.
Thanks very much to point out I could actually print the colormap
definition-data.
I printed all of them, and found out the colormaps invoking errors are
all tuples but not dictionaries and all other colormaps are actually
dictionaries.
###Examples without Errors###
###They are all dictionaries###
print matplotlib._cm._gist_stern_data
{'blue': ((0.0, 0.0, 0.0), (0.5, 1.0, 1.0), (0.73499999999999999, 0.0,
0.0), (1.0, 1.0, 1.0)), 'green': ((0, 0, 0), (1, 1, 1)), 'red': ((0.0,
0.0, 0.0), (0.054699999999999999, 1.0, 1.0), (0.25, 0.027, 0.25),
(1.0, 1.0, 1.0))}
print matplotlib._cm._jet_data
{'blue': ((0.0, 0.5, 0.5), (0.11, 1, 1), (0.34000000000000002, 1, 1),
(0.65000000000000002, 0, 0), (1, 0, 0)), 'green': ((0.0, 0, 0),
(0.125, 0, 0), (0.375, 1, 1), (0.64000000000000001, 1, 1),
(0.91000000000000003, 0, 0), (1, 0, 0)), 'red': ((0.0, 0, 0),
(0.34999999999999998, 0, 0), (0.66000000000000003, 1, 1),
(0.89000000000000001, 1, 1), (1, 0.5, 0.5))}
###Colormaps invoking Errors###
###They are all Tuples###
Problems to create gist_rainbow
((0.0, (1.0, 0.0, 0.16)), (0.029999999999999999, (1.0, 0.0, 0.0)),
(0.215, (1.0, 1.0, 0.0)), (0.40000000000000002, (0.0, 1.0, 0.0)),
(0.58599999999999997, (0.0, 1.0, 1.0)), (0.77000000000000002, (0.0,
0.0, 1.0)), (0.95399999999999996, (1.0, 0.0, 1.0)), (1.0, (1.0, 0.0,
0.75)))
The error was --> <type 'exceptions.TypeError'>: tuple indices must be
integers, not str
Problems to create terrain
((0.0, (0.20000000000000001, 0.20000000000000001,
0.59999999999999998)), (0.14999999999999999, (0.0,
0.59999999999999998, 1.0)), (0.25, (0.0, 0.80000000000000004,
0.40000000000000002)), (0.5, (1.0, 1.0, 0.59999999999999998)), (0.75,
(0.5, 0.35999999999999999, 0.33000000000000002)), (1.0, (1.0, 1.0,
1.0)))
The error was --> <type 'exceptions.TypeError'>: tuple indices must be
integers, not str
Problems to create bwr
((0.0, 0.0, 1.0), (1.0, 1.0, 1.0), (1.0, 0.0, 0.0))
The error was --> <type 'exceptions.TypeError'>: tuple indices must be
integers, not str
Problems to create brg
((0.0, 0.0, 1.0), (1.0, 0.0, 0.0), (0.0, 1.0, 0.0))
The error was --> <type 'exceptions.TypeError'>: tuple indices must be
integers, not str
Problems to create seismic
((0.0, 0.0, 0.29999999999999999), (0.0, 0.0, 1.0), (1.0, 1.0, 1.0),
(1.0, 0.0, 0.0), (0.5, 0.0, 0.0))
The error was --> <type 'exceptions.TypeError'>: tuple indices must be
integers, not str
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