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How to get the nth element of a python list or a default if not available
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gruszczygruszczy
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Pass a data.frame column name to a function
... just use the column name directly:
df <- data.frame(A=1:10, B=2:11, C=3:12)
fun1 <- function(x, column){
max(x[,column])
}
fun1(df, "B")
fun1(df, c("B","A"))
There's no need to use substitute, eval, etc.
You can even pass the desired function as a parameter:
fun1 <- function(x, colu...
Numpy array dimensions
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513
It is .shape:
ndarray.shape
Tuple of array dimensions.
Thus:
>>> a.shape
(2, 2...
汇编语言（王爽著）附书签 - 文档下载 - 清泛网 - 专注C/C++及内核技术
...自己学，看了很多书，国内像这样的好书真的是很难得。3、更珍贵的是老师的编排，可以说比国外的还好（当然从知识点来说不如国外的书，但是这是一本入门书）
我的感想：1、计算机科学方面的好书，中国基本上没有（运...
Why can't R's ifelse statements return vectors?
...tors, you will get longer results:
> ifelse(c(TRUE, FALSE), c(1, 2), c(3, 4))
[1] 1 4
So ifelse is intended for the specific purpose of testing a vector of booleans and returning a vector of the same length, filled with elements taken from the (vector) yes and no arguments.
It is a common con...
Repeat each row of data.frame the number of times specified in a column
...), 1:2]
Result:
var1 var2
1 a d
2 b e
2.1 b e
3 c f
3.1 c f
3.2 c f
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What's the difference between lists enclosed by square brackets and parentheses in Python?
...you can change its contents:
>>> x = [1,2]
>>> x.append(3)
>>> x
[1, 2, 3]
while tuples are not:
>>> x = (1,2)
>>> x
(1, 2)
>>> x.append(3)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
AttributeError: '...
Python “extend” for a dictionary
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phoenix
3,20611 gold badge2727 silver badges3131 bronze badges
answered Feb 23 '09 at 11:01
Nick FortescueNic...
Pandas groupby: How to get a union of strings
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In [5]: df
Out[5]:
A B C
0 1 0.749065 This
1 2 0.301084 is
2 3 0.463468 a
3 4 0.643961 random
4 1 0.866521 string
5 2 0.120737 !
In [6]: df.dtypes
Out[6]:
A int64
B float64
C object
dtype: object
When you apply your own function, t...