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r - Convert data.frame column format from character to factor

I would like to change the format (class) of some columns of my data.frame object (mydf) from charactor to ... .table() function. Any help would be appreciated. Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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What is the purpose of flush() in Java streams?

In Java, flush() method is used in streams. But I don't understand what are all the purpose of using this method? fin.flush(); tell me some suggestions. Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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224 views

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string to string array conversion in java

I have a string = "name"; I want to convert into a string array. How do I do it? Is there any java built in ... 'n' will be now string "n" stored in an array. Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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mysql - #1071 - Specified key was too long; max key length is 1000 bytes

I know questions with this title have been answered before, but please do read on. I've read thoroughly all ... . Any clue appreciated. I'm using phpMyAdmin. Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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iphone - To ARC or not to ARC? What are the pros and cons?

Closed. This question needs to be more focused. It is not currently accepting answers. Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c# - How do I use WebRequest to access an SSL encrypted site using HTTPS?

I'm writing a program that reads content from a user provided URL. My problem is in the code that goes ... it will work with SSL encrypted content. Thanks. Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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Displaying the #include hierarchy for a C++ file in Visual Studio

Problem: I have a large Visual C++ project that I'm trying to migrate to Visual Studio 2010. It's a ... h(100) winsock.h some_other_thing.h(1234) winsock2.h Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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Using CMake with GNU Make: How can I see the exact commands?

I use CMake with GNU Make and would like to see all commands exactly (for example how the compiler is ... flags in the generated Makefile for debugging purpose? Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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sql - SELECT DISTINCT on one column

Using SQL Server, I have... ID SKU PRODUCT ======================= 1 FOO-23 Orange 2 BAR-23 Orange 3 FOO ... TestData] WHERE ([SKU] LIKE 'FOO-%')) ORDER BY [ID] Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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android - How to create directory automatically on SD card

I'm trying to save my file to the following location FileOutputStream fos = new FileOutputStream("/sdcard/ ... a directory and sub-directory using code? Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c# - Handling warning for possible multiple enumeration of IEnumerable

In my code I need to use an IEnumerable<> several times, resulting in the ReSharper error of "Possible multiple ... awkward. What would you do in this scenario? Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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jakarta ee - What does the servlet <load-on-startup> value signify

I am getting a bit confused here. In our application we are having a few servlets defined. Here is the excerpt ... I came across only added to my confusion. Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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Why are C++ inline functions in the header?

NB This is not a question about how to use inline functions or how they work, more why they are done ... .exe : fatal error LNK1120: 1 unresolved externals Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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Can constructors throw exceptions in Java?

Are constructors allowed to throw exceptions? Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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node.js - How can I save a base64-encoded image to disk?

My Express app is receiving a base64-encoded PNG from the browser (generated from canvas with toDataURL() ) and writing it ... , but it's not a valid image }); Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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Can I install Python windows packages into virtualenvs?

Virtualenv is great: it lets me keep a number of distinct Python installations so that different projects' ... direct it to install into the virtualenv? Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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.net - Conditionally use 32/64 bit reference when building in Visual Studio

I have a project that builds in 32/64-bit and has corresponding 32/64-bit dependencies. I want to be able ... and have the referenced DLL be the right bitness. Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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192 views

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How to prevent a jQuery Ajax request from caching in Internet Explorer?

How do I prevent a jQuery Ajax request from caching in Internet Explorer? Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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360 views

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c++ - What is the difference between conversion specifiers %i and %d in formatted IO functions (*printf / *scanf)

What is the difference between %d and %i when used as format specifiers in printf and scanf? Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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236 views

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android - More than one file was found with OS independent path 'META-INF/LICENSE'

When I build my app, I get the following error: Error: Execution failed for task ':app: ... Who has ideas how to solve this? Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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439 views

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c - Is errno thread-safe?

In errno.h, this variable is declared as extern int errno; so my question is, is it safe to check errno ... I am using linux with gcc on x86 architecture. Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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283 views

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c++ - Deleting elements from std::set while iterating

I need to go through a set and remove elements that meet a predefined criteria. This is the test code I ... making the code less error-prone and more readable. Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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547 views

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ASP.NET: Session.SessionID changes between requests

Why does the property SessionID on the Session-object in an ASP.NET-page change between requests? I have a page ... every time I hit F5, independent of browser. Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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255 views

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.net - What's the difference between ViewData and ViewBag?

I saw the ViewBag in MVC 3. How's that different than ViewData in MVC 2? Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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197 views

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Why is String.chars() a stream of ints in Java 8?

In Java 8, there is a new method String.chars() which returns a stream of ints (IntStream) that represent the ... was the motivation to design the API this way? Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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181 views

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Pretty printing XML with javascript

I have a string that represents a non indented XML that I would like to pretty-print. For example: <root><node/> ... is this to be done on the client side. Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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253 views

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java - Limit Decimal Places in Android EditText

I'm trying to write an app that helps you manage your finances. I'm using an EditText Field where the ... number of characters after the decimal point to two? Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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214 views

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java - How to run certain task every day at a particular time using ScheduledExecutorService?

I am trying to run a certain task everyday at 5 AM in the morning. So I decided to use ... also TimerTask is better for this or ScheduledExecutorService? Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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