Matplotlib в при сохранении PDF

Question

У меня есть следующий код Python:

import numpy as np 
import sklearn as sk 
import pandas as pd 
import scipy as sp 
import matplotlib.pyplot as plt 
import sys 
from sklearn.decomposition import PCA 
from sklearn.svm import OneClassSVM 



np.random.seed(0) 

x1 = np.random.normal((1,1), 0.1, (200, 2)) 
x2 = np.random.normal((1,0), .1, (200, 2)) 
x3 = np.random.normal((0,1), .1, (200, 2)) 
x4 = np.array([[0.5, 0.5], 
       [0.5, 1], 
       [1, 0.5]]) 


X = np.vstack([x1, x2, x3])#, x4]) 
X = sk.preprocessing.scale(X) 

X_new = np.vstack([x1, x2, x3, x4]) 
X_new = sk.preprocessing.scale(X_new) 



n, p = X_new.shape 

anomaly_index = np.array(range(n-3, n)) 
normal_index = np.array(range(n-3)) 

#plt.scatter(X_new[normal_index,0], X_new[normal_index,1]) 
#plt.scatter(X_new[anomaly_index,0], X_new[anomaly_index,1], marker='*', c='r') 
#plt.show() 


gammas = [0.5]#, 0.7, 0.9] 
nus = [0.01]#, 0.3, 0.8] 
nrow = len(gammas) 
ncol = len(nus) 


j = 0 
for gamma in gammas: 
    for nu in nus: 
     j += 1 

     svm = OneClassSVM(kernel='rbf', degree=2, 
          gamma=gamma, coef0=0.0, 
          tol=0.001, 
          nu=nu, shrinking=True, 
          cache_size=200, 
          verbose=False, 
          max_iter=-1, random_state=None) 
     svm.fit(X) 

     anomaly_score = - svm.decision_function(X_new) 
     vmin = anomaly_score.min() 
     vmax = anomaly_score.max() 


     xx1, yy1 = np.meshgrid(np.linspace(X_new[:,0].min()-0.3, 
              X_new[:,0].max()+0.3, 1000), 
           np.linspace(X_new[:,1].min()-0.3, 
              X_new[:,1].max()+0.3, 1000)) 
     Z1 = svm.decision_function(np.c_[xx1.ravel(), yy1.ravel()]) 
     Z1 = Z1.reshape(xx1.shape) 



     plt.subplot(nrow, ncol, j) 
     plt.title(r'$\gamma=$' + str(gamma) + r' $\nu=$' + str(nu) + '') 
     plt.scatter(X_new[normal_index, 0], X_new[normal_index, 1], 
        c=anomaly_score[normal_index], alpha=2, s=50, 
        vmin=vmin, vmax=vmax) 
     plt.scatter(X_new[anomaly_index, 0], 
        X_new[anomaly_index, 1], marker='*', 
        c=anomaly_score[anomaly_index], alpha=2, s=90, 
        vmin=vmin, vmax=vmax) 

     plt.colorbar() 
     #cb = plt.colorbar() 
     #tick_locator = ticker.MaxNLocator(nbins=5) 
     #cb.locator = tick_locator 
     #cb.update_ticks() 

     plt.contourf(xx1, yy1, Z1, cmap=plt.cm.Blues, 
         levels=np.linspace(Z1.min(), 0.3, 7), alpha=0.1) 
     plt.xlim(X_new[:,0].min()-0.3, X_new[:, 0].max()+0.3) 
     plt.ylim(X_new[:,1].min()-0.3, X_new[:, 1].max()+0.3) 
     plt.xlabel(r'$x_1$', size=20) 
     plt.ylabel(r'$x_2$', size=20) 
     plt.locator_params(nbins=4) 
     plt.tight_layout() 
#plt.savefig('one_class_svm_3_clusters_grid.pdf') 
plt.show() 

Это прекрасно работает, но если я раскомментировать plt.savefig я получаю следующее сообщение об ошибке:

Process Python[/home/donbeo/Documents/pythoncode/fault_detection/one_class_svm/oc_svm_3_clusters.py] finished 
Python 3.4.0 (default, Jun 19 2015, 14:20:21) 
[GCC 4.8.2] on linux 
Type "help", "copyright", "credits" or "license" for more information. 
>>> >>> >>> >>> >>> 

Process Python[/home/donbeo/Documents/pythoncode/fault_detection/one_class_svm/oc_svm_3_clusters.py] finished 
Python 3.4.0 (default, Jun 19 2015, 14:20:21) 
[GCC 4.8.2] on linux 
Type "help", "copyright", "credits" or "license" for more information. 
>>> >>> >>> >>> Traceback (most recent call last): 
    File "/usr/local/lib/python3.4/dist-packages/matplotlib/colors.py", line 355, in to_rgba 
    'number in rbga sequence outside 0-1 range') 
ValueError: number in rbga sequence outside 0-1 range 

During handling of the above exception, another exception occurred: 

Traceback (most recent call last): 
    File "<stdin>", line 1, in <module> 
    File "/home/donbeo/Documents/pythoncode/fault_detection/one_class_svm/oc_svm_3_clusters.py", line 98, in <module> 
    plt.savefig(plot_path + 'one_class_svm_3_clusters_grid.pdf') 
    File "/usr/local/lib/python3.4/dist-packages/matplotlib/pyplot.py", line 577, in savefig 
    res = fig.savefig(*args, **kwargs) 
    File "/usr/local/lib/python3.4/dist-packages/matplotlib/figure.py", line 1476, in savefig 
    self.canvas.print_figure(*args, **kwargs) 
    File "/usr/local/lib/python3.4/dist-packages/matplotlib/backends/backend_qt5agg.py", line 161, in print_figure 
    FigureCanvasAgg.print_figure(self, *args, **kwargs) 
    File "/usr/local/lib/python3.4/dist-packages/matplotlib/backend_bases.py", line 2211, in print_figure 
    **kwargs) 
    File "/usr/local/lib/python3.4/dist-packages/matplotlib/backends/backend_pdf.py", line 2485, in print_pdf 
    self.figure.draw(renderer) 
    File "/usr/local/lib/python3.4/dist-packages/matplotlib/artist.py", line 59, in draw_wrapper 
    draw(artist, renderer, *args, **kwargs) 
    File "/usr/local/lib/python3.4/dist-packages/matplotlib/figure.py", line 1085, in draw 
    func(*args) 
    File "/usr/local/lib/python3.4/dist-packages/matplotlib/artist.py", line 59, in draw_wrapper 
    draw(artist, renderer, *args, **kwargs) 
    File "/usr/local/lib/python3.4/dist-packages/matplotlib/axes/_base.py", line 2110, in draw 
    a.draw(renderer) 
    File "/usr/local/lib/python3.4/dist-packages/matplotlib/artist.py", line 59, in draw_wrapper 
    draw(artist, renderer, *args, **kwargs) 
    File "/usr/local/lib/python3.4/dist-packages/matplotlib/collections.py", line 772, in draw 
    Collection.draw(self, renderer) 
    File "/usr/local/lib/python3.4/dist-packages/matplotlib/artist.py", line 59, in draw_wrapper 
    draw(artist, renderer, *args, **kwargs) 
    File "/usr/local/lib/python3.4/dist-packages/matplotlib/collections.py", line 320, in draw 
    self._offset_position) 
    File "/usr/local/lib/python3.4/dist-packages/matplotlib/backends/backend_pdf.py", line 1658, in draw_path_collection 
    antialiaseds, urls, offset_position): 
    File "/usr/local/lib/python3.4/dist-packages/matplotlib/backend_bases.py", line 488, in _iter_collection 
    gc0.set_foreground(fg) 
    File "/usr/local/lib/python3.4/dist-packages/matplotlib/backend_bases.py", line 1008, in set_foreground 
    self._rgb = colors.colorConverter.to_rgba(fg) 
    File "/usr/local/lib/python3.4/dist-packages/matplotlib/colors.py", line 376, in to_rgba 
    'to_rgba: Invalid rgba arg "%s"\n%s' % (str(arg), exc)) 
ValueError: to_rgba: Invalid rgba arg "[ 0. 0. 0. 2.]" 
number in rbga sequence outside 0-1 range 
>>> 

Answer 1

Посмотрите на сообщение об ошибке, оно сообщает вам, что не так. Последняя линия вашего TRACEBACK показывает, что альфа (четвертое значение) вашего RGBA цвета имеет значение 2, в то время как оно должно быть между 0 и 1.

В качестве небольшого примера,

x1 = np.random.normal((1,1), 0.1, (200, 2)) 
plt.scatter(x1[:,0], x1[:,1], alpha=2) 
plt.show() 

даст то же сообщение об ошибке. Просто замените значение альфа на число между 0 и 1, а ошибка уходит:

x1 = np.random.normal((1,1), 0.1, (200, 2)) 
plt.scatter(x1[:,0], x1[:,1], alpha=0.5) 
plt.show() 

В коде, измените значение альфа в следующих строках. Здесь я заменил его на 0,5, но вы можете выбрать то, что хотите, если оно находится между 0 и 1.

plt.scatter(X_new[normal_index, 0], X_new[normal_index, 1], 
       c=anomaly_score[normal_index], alpha=0.5, s=50, 
       vmin=vmin, vmax=vmax) 
plt.scatter(X_new[anomaly_index, 0], 
       X_new[anomaly_index, 1], marker='*', 
       c=anomaly_score[anomaly_index], alpha=0.5, s=90, 
       vmin=vmin, vmax=vmax)