Python 中 X = X[:, 1] 的含义
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Meaning of X = X[:, 1] in Python
提问by Taewan
I am studying this snippet of python code. What does X = X[:, 1]mean in last line?
我正在研究这段python代码。X = X[:, 1]最后一行是什么意思？
def linreg(X,Y):
# Running the linear regression
X = sm.add_constant(X)
model = regression.linear_model.OLS(Y, X).fit()
a = model.params[0]
b = model.params[1]
X = X[:, 1]
采纳答案by Leb
x = np.random.rand(3,2)
x
Out[37]:
array([[ 0.03196827, 0.50048646],
[ 0.85928802, 0.50081615],
[ 0.11140678, 0.88828011]])
x = x[:,1]
x
Out[39]: array([ 0.50048646, 0.50081615, 0.88828011])
So what that line did is slicedthe array, taking all rows (:) but keeping the second column (1)
那么该行所做的是对数组进行切片，取所有行 ( :) 但保留第二列 ( 1)
回答by S L SREEJITH
it is simply like you are specifying the axis. Consider the starting column as 0 then as you go through 1,2 and so on.
就像您指定轴一样。将起始列视为 0，然后在您通过 1,2 等时。
The syntax is x[row_index,column_index]
语法是 x[row_index,column_index]
you can also specify a range of row values as per need in row_index also eg:1:13 extracts first 13 rows along with whatever specified in column
您还可以根据需要在 row_index 中指定一系列行值，例如：1:13 提取前 13 行以及列中指定的任何内容
回答by Adiraamruta
Something you shoud know
你应该知道的事
The term you need to search for is slice. x[start:end:step]is the full form, Here we can omit to use a default value: start defaults to 0 , end defaults to the length of the list, and step defaults to 1. And hence x[:] means same as x[0:len(x):1]
您需要搜索的术语是切片。 x[start:end:step]是完整形式，这里我们可以省略使用默认值：start 默认为 0 ，end 默认为列表的长度，step 默认为 1。因此 x[:] 表示与 x[0:len(x):1] 相同
