我准备使用python写一个制作四维柱状图的代码，现在遇到了一些问题，请各位大侠高手指点，有偿！！
我有4列数据，前3列是属性，第4列是类别（+1，-1），我希望三个属性代表x,y,z，并且使用柱状图表示，柱状图的颜色代表类型（两种颜色）。
我的代码出错的部分如下：
read txt file
def Detectionplot():
data = pd.read_csv('D:\\ML\M316-svm-test.txt', sep = '\t', encoding = 'utf-8')
m = data['data']
fig = plt.figure()
ax = fig.subplot(111, projection='3d') # multiple maps using add_subplot
x = []
y = []
z = []
r = [] # 'r' is not defined r代表类别，为+1或-1
x = x.flatten('F')
y = y.flatten('F')
运行代码出错如下：
Python 3.7.0b4 (v3.7.0b4:eb96c37699, May 2 2018, 19:02:22) [MSC v.1913 64 bit (AMD64)] on win32
Type "copyright", "credits" or "license()" for more information.
================== RESTART: D:\ML\python3.7\4Dcolumnmap.py ==================
Traceback (most recent call last):
File "D:\ML\python3.7\4Dcolumnmap.py", line 32, in
for a in r:
NameError: name 'r' is not defined
请各位高手大侠出手相助，万分感谢！
