大约有 41,000 项符合查询结果（耗时：0.0250秒） [XML]
Dynamically select data frame columns using $ and a character value
...is a reproducible example below:
# set seed for reproducibility
set.seed(123)
df <- data.frame( col1 = sample(5,10,repl=T) , col2 = sample(5,10,repl=T) , col3 = sample(5,10,repl=T) )
# We want to sort by 'col3' then by 'col1'
sort_list <- c("col3","col1")
# Use 'do.call' to call order. S...
How to overwrite the previous print to stdout in python?
...
123
One way is to use the carriage return ('\r') character to return to the start of the line with...
Can an html element have multiple ids?
...answered Apr 16 '11 at 7:53
user123444555621user123444555621
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Is it possible to stop JavaScript execution? [duplicate]
...
123
You can make a JavaScript typo :D (thinking outside the box here)
thisFunctionDoesNotExistAnd...
What are the details of “Objective-C Literals” mentioned in the Xcode 4.4 release notes?
...;
number = [NSNumber numberWithChar:'X'];
number = [NSNumber numberWithInt:12345];
number = [NSNumber numberWithUnsignedLong:12345ul];
number = [NSNumber numberWithLongLong:12345ll];
number = [NSNumber numberWithFloat:123.45f];
number = [NSNumber numberWithDouble:123.45];
number = [NSNumber numberWi...
通信连接组件 · App Inventor 2 中文网
...开浏览器到指定的网页。 假设您要访问的页面是“www.fun123.cn”（您可以随意替换自己的选择），将属性设置为：
Action: android.intent.action.VIEW
DataUri: http://www.fun123.cn
调用第三方地图也可以使用这个启动器：
...
How to check if a Unix .tar.gz file is a valid file without uncompressing?
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123
What about just getting a listing of the tarball and throw away the output, rather than decomp...
When to use @QueryParam vs @PathParam
...blog I request
GET: myserver.com/myblog/posts
to get the post with id = 123, I would request
GET: myserver.com/myblog/posts/123
but to filter my list of posts, and get all posts since Jan 1, 2013, I would request
GET: myserver.com/myblog/posts?since=2013-01-01
In the first example "posts" i...
Error installing mysql2: Failed to build gem native extension
...t be 127.0.0.1, and if the password is number, it must be put in quote ex '123456' otherwise we can type normally ex admin123
– duykhoa
Oct 30 '12 at 7:46
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What data type to use for money in Java? [closed]
...yAmount = amountFactory.setCurrency(Monetary.getCurrency("EUR")).setNumber(12345.67).create();
MonetaryAmountFormat format = MonetaryFormats.getAmountFormat(Locale.getDefault());
System.out.println(format.format(monetaryAmount));
When using the reference implementation API, the necessary code is m...