大约有 1,641 项符合查询结果（耗时：0.0219秒） [XML]
Determine the number of NA values in a column
... In counting amount of arbitrary value, other than NA is writing a boolean function is.value and then using sum(is.value(df$col)) the way to go or is there a more concise direct syntax for this?
– user3274289
Jun 4 '14 at 2:11
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Getting the first index of an object
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Just for fun this works in JS 1.8.5
var obj = {a: 1, b: 2, c: 3};
Object.keys(obj)[0]; // "a"
This matches the same order that you would see doing
for (o in obj) { ... }
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How do I extract text that lies between parentheses (round brackets)?
...e (sales)", @"\(([^)]*)\)").Groups[1].Value
As a response to the (very funny) comment, here's the same Regex with some explanation:
\( # Escaped parenthesis, means "starts with a '(' character"
( # Parentheses in a regex mean "put (capture) the stuff
# ...
How to check whether a file is empty or not?
...size() and stat() will throw an exception if the file does not exist. This function will return True/False without throwing (simpler but less robust):
import os
def is_non_zero_file(fpath):
return os.path.isfile(fpath) and os.path.getsize(fpath) > 0
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App Inventor 2 试验组件 · App Inventor 2 中文网
...用 隐私策略和使用条款 技术支持 service@fun123.cn
What's the best/easiest GUI Library for Ruby? [closed]
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Shoes is not made for production environment but for fun, it is the "turtle graphic" of Ruby. It is intended for newbies to get acquainted with 1.) domain specific language, 2.) graphics
– karatedog
Feb 2 '12 at 11:58
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Android and setting width and height programmatically in dp units
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@RomainGuy, can you please add a utility function to the API to convert from dp to px? Thanks.
– AlikElzin-kilaka
May 6 '13 at 14:22
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How do I close all open tabs at once?
...-9
Do not use it. It does what you ask but probably not the best way but fun way
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Width equal to content [duplicate]
... caniuse.com/#search=max-content Agree with @pkr298 Just use for 'fun' stuff - not production.
– CodeFinity
Feb 1 '18 at 15:27
1
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云数据及Firebase组件简介 · App Inventor 2 中文网
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