我能从决策树中的训练树中提取基本的决策规则(或“决策路径”)作为文本列表吗?
喜欢的东西:
if A>0.4 then if B<0.2 then if C>0.8 then class='X'
我能从决策树中的训练树中提取基本的决策规则(或“决策路径”)作为文本列表吗?
喜欢的东西:
if A>0.4 then if B<0.2 then if C>0.8 then class='X'
当前回答
下面是一个通过转换export_text的输出从决策树生成Python代码的函数:
import string
from sklearn.tree import export_text
def export_py_code(tree, feature_names, max_depth=100, spacing=4):
if spacing < 2:
raise ValueError('spacing must be > 1')
# Clean up feature names (for correctness)
nums = string.digits
alnums = string.ascii_letters + nums
clean = lambda s: ''.join(c if c in alnums else '_' for c in s)
features = [clean(x) for x in feature_names]
features = ['_'+x if x[0] in nums else x for x in features if x]
if len(set(features)) != len(feature_names):
raise ValueError('invalid feature names')
# First: export tree to text
res = export_text(tree, feature_names=features,
max_depth=max_depth,
decimals=6,
spacing=spacing-1)
# Second: generate Python code from the text
skip, dash = ' '*spacing, '-'*(spacing-1)
code = 'def decision_tree({}):\n'.format(', '.join(features))
for line in repr(tree).split('\n'):
code += skip + "# " + line + '\n'
for line in res.split('\n'):
line = line.rstrip().replace('|',' ')
if '<' in line or '>' in line:
line, val = line.rsplit(maxsplit=1)
line = line.replace(' ' + dash, 'if')
line = '{} {:g}:'.format(line, float(val))
else:
line = line.replace(' {} class:'.format(dash), 'return')
code += skip + line + '\n'
return code
示例用法:
res = export_py_code(tree, feature_names=names, spacing=4)
print (res)
样例输出:
def decision_tree(f1, f2, f3):
# DecisionTreeClassifier(class_weight=None, criterion='gini', max_depth=3,
# max_features=None, max_leaf_nodes=None,
# min_impurity_decrease=0.0, min_impurity_split=None,
# min_samples_leaf=1, min_samples_split=2,
# min_weight_fraction_leaf=0.0, presort=False,
# random_state=42, splitter='best')
if f1 <= 12.5:
if f2 <= 17.5:
if f1 <= 10.5:
return 2
if f1 > 10.5:
return 3
if f2 > 17.5:
if f2 <= 22.5:
return 1
if f2 > 22.5:
return 1
if f1 > 12.5:
if f1 <= 17.5:
if f3 <= 23.5:
return 2
if f3 > 23.5:
return 3
if f1 > 17.5:
if f1 <= 25:
return 1
if f1 > 25:
return 2
上面的示例生成了names = ['f'+str(j+1) for j in range(NUM_FEATURES)]。
一个方便的功能是,它可以生成更小的文件大小与减少间距。只需要设置spacing=2。
其他回答
下面是一个函数,在python3下打印scikit-learn决策树的规则,并对条件块进行偏移,使结构更具可读性:
def print_decision_tree(tree, feature_names=None, offset_unit=' '):
'''Plots textual representation of rules of a decision tree
tree: scikit-learn representation of tree
feature_names: list of feature names. They are set to f1,f2,f3,... if not specified
offset_unit: a string of offset of the conditional block'''
left = tree.tree_.children_left
right = tree.tree_.children_right
threshold = tree.tree_.threshold
value = tree.tree_.value
if feature_names is None:
features = ['f%d'%i for i in tree.tree_.feature]
else:
features = [feature_names[i] for i in tree.tree_.feature]
def recurse(left, right, threshold, features, node, depth=0):
offset = offset_unit*depth
if (threshold[node] != -2):
print(offset+"if ( " + features[node] + " <= " + str(threshold[node]) + " ) {")
if left[node] != -1:
recurse (left, right, threshold, features,left[node],depth+1)
print(offset+"} else {")
if right[node] != -1:
recurse (left, right, threshold, features,right[node],depth+1)
print(offset+"}")
else:
print(offset+"return " + str(value[node]))
recurse(left, right, threshold, features, 0,0)
显然,很久以前就有人决定尝试将以下函数添加到官方scikit的树导出函数中(基本上只支持export_graphviz)
def export_dict(tree, feature_names=None, max_depth=None) :
"""Export a decision tree in dict format.
以下是他的全部承诺:
https://github.com/scikit-learn/scikit-learn/blob/79bdc8f711d0af225ed6be9fdb708cea9f98a910/sklearn/tree/export.py
不太确定这条评论发生了什么。但是你也可以尝试使用这个函数。
我认为这为scikit-learn的优秀人员提供了一个严肃的文档需求,以正确地记录sklearn.tree.Tree API,这是一个底层的树结构,DecisionTreeClassifier将其作为属性tree_公开。
这是基于@paulkernfeld的回答。如果你有一个包含特征的数据框架X和一个包含共振的目标数据框架y,你想知道哪个y值结束于哪个节点(并相应地绘制它),你可以做以下工作:
def tree_to_code(tree, feature_names):
from sklearn.tree import _tree
codelines = []
codelines.append('def get_cat(X_tmp):\n')
codelines.append(' catout = []\n')
codelines.append(' for codelines in range(0,X_tmp.shape[0]):\n')
codelines.append(' Xin = X_tmp.iloc[codelines]\n')
tree_ = tree.tree_
feature_name = [
feature_names[i] if i != _tree.TREE_UNDEFINED else "undefined!"
for i in tree_.feature
]
#print "def tree({}):".format(", ".join(feature_names))
def recurse(node, depth):
indent = " " * depth
if tree_.feature[node] != _tree.TREE_UNDEFINED:
name = feature_name[node]
threshold = tree_.threshold[node]
codelines.append ('{}if Xin["{}"] <= {}:\n'.format(indent, name, threshold))
recurse(tree_.children_left[node], depth + 1)
codelines.append( '{}else: # if Xin["{}"] > {}\n'.format(indent, name, threshold))
recurse(tree_.children_right[node], depth + 1)
else:
codelines.append( '{}mycat = {}\n'.format(indent, node))
recurse(0, 1)
codelines.append(' catout.append(mycat)\n')
codelines.append(' return pd.DataFrame(catout,index=X_tmp.index,columns=["category"])\n')
codelines.append('node_ids = get_cat(X)\n')
return codelines
mycode = tree_to_code(clf,X.columns.values)
# now execute the function and obtain the dataframe with all nodes
exec(''.join(mycode))
node_ids = [int(x[0]) for x in node_ids.values]
node_ids2 = pd.DataFrame(node_ids)
print('make plot')
import matplotlib.cm as cm
colors = cm.rainbow(np.linspace(0, 1, 1+max( list(set(node_ids)))))
#plt.figure(figsize=cm2inch(24, 21))
for i in list(set(node_ids)):
plt.plot(y[node_ids2.values==i],'o',color=colors[i], label=str(i))
mytitle = ['y colored by node']
plt.title(mytitle ,fontsize=14)
plt.xlabel('my xlabel')
plt.ylabel(tagname)
plt.xticks(rotation=70)
plt.legend(loc='upper center', bbox_to_anchor=(0.5, 1.00), shadow=True, ncol=9)
plt.tight_layout()
plt.show()
plt.close
不是最优雅的版本,但它做到了…
只需使用sklearn中的函数。像这样的树
from sklearn.tree import export_graphviz
export_graphviz(tree,
out_file = "tree.dot",
feature_names = tree.columns) //or just ["petal length", "petal width"]
然后在项目文件夹中查找文件树。点,复制所有的内容,并粘贴到这里http://www.webgraphviz.com/,并生成您的图形:)
我需要一种更人性化的决策树规则格式。我正在构建开源AutoML Python包,很多时候MLJAR用户希望从树中看到确切的规则。
这就是为什么我实现了一个基于paulkernfeld答案的函数。
def get_rules(tree, feature_names, class_names):
tree_ = tree.tree_
feature_name = [
feature_names[i] if i != _tree.TREE_UNDEFINED else "undefined!"
for i in tree_.feature
]
paths = []
path = []
def recurse(node, path, paths):
if tree_.feature[node] != _tree.TREE_UNDEFINED:
name = feature_name[node]
threshold = tree_.threshold[node]
p1, p2 = list(path), list(path)
p1 += [f"({name} <= {np.round(threshold, 3)})"]
recurse(tree_.children_left[node], p1, paths)
p2 += [f"({name} > {np.round(threshold, 3)})"]
recurse(tree_.children_right[node], p2, paths)
else:
path += [(tree_.value[node], tree_.n_node_samples[node])]
paths += [path]
recurse(0, path, paths)
# sort by samples count
samples_count = [p[-1][1] for p in paths]
ii = list(np.argsort(samples_count))
paths = [paths[i] for i in reversed(ii)]
rules = []
for path in paths:
rule = "if "
for p in path[:-1]:
if rule != "if ":
rule += " and "
rule += str(p)
rule += " then "
if class_names is None:
rule += "response: "+str(np.round(path[-1][0][0][0],3))
else:
classes = path[-1][0][0]
l = np.argmax(classes)
rule += f"class: {class_names[l]} (proba: {np.round(100.0*classes[l]/np.sum(classes),2)}%)"
rule += f" | based on {path[-1][1]:,} samples"
rules += [rule]
return rules
规则按照分配给每个规则的训练样本的数量进行排序。对于每条规则,都有关于预测的类名和分类任务预测概率的信息。对于回归任务,只打印关于预测值的信息。
例子
from sklearn import datasets
from sklearn.tree import DecisionTreeRegressor
from sklearn import tree
# Prepare the data data
boston = datasets.load_boston()
X = boston.data
y = boston.target
# Fit the regressor, set max_depth = 3
regr = DecisionTreeRegressor(max_depth=3, random_state=1234)
model = regr.fit(X, y)
# Print rules
rules = get_rules(regr, boston.feature_names, None)
for r in rules:
print(r)
印刷规则:
if (RM <= 6.941) and (LSTAT <= 14.4) and (DIS > 1.385) then response: 22.905 | based on 250 samples
if (RM <= 6.941) and (LSTAT > 14.4) and (CRIM <= 6.992) then response: 17.138 | based on 101 samples
if (RM <= 6.941) and (LSTAT > 14.4) and (CRIM > 6.992) then response: 11.978 | based on 74 samples
if (RM > 6.941) and (RM <= 7.437) and (NOX <= 0.659) then response: 33.349 | based on 43 samples
if (RM > 6.941) and (RM > 7.437) and (PTRATIO <= 19.65) then response: 45.897 | based on 29 samples
if (RM <= 6.941) and (LSTAT <= 14.4) and (DIS <= 1.385) then response: 45.58 | based on 5 samples
if (RM > 6.941) and (RM <= 7.437) and (NOX > 0.659) then response: 14.4 | based on 3 samples
if (RM > 6.941) and (RM > 7.437) and (PTRATIO > 19.65) then response: 21.9 | based on 1 samples
我在我的文章中总结了从决策树中提取规则的方法:用Scikit-Learn和Python以3种方式从决策树中提取规则。