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r - Compare two data.frames to find the rows in data.frame 1 that are not present in data.frame 2

I have the following 2 data.frames: a1 <- data.frame(a = 1:5, b=letters[1:5]) a2 <- data.frame(a = 1:3, b= ... .a2.rows) } rows.in.a1.that.are.not.in.a2(a1,a2) Question&Answers:os...

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

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r - Fastest way to replace NAs in a large data.table

I have a large data.table, with many missing values scattered throughout its ~200k rows and 200 columns. I would like ... to a data.table won't take too long. Question&Answers:os...

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

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What is the equivalent of ngShow and ngHide in Angular 2+?

I have a number of elements that I want to be visible under certain conditions. In AngularJS I would write <div ng-show ... > How can I do this in Angular 2+? Question&Answers:os...

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

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asp.net mvc - MVC 4 Razor File Upload

I am new to MVC 4 and I am trying to implement File Upload Control in my website. I am not able to find the ... name="Submit" id="Submit" value="Upload" /> } Question&Answers:os...

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

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android - Emulator: ERROR: x86 emulation currently requires hardware acceleration

I tried to run my Hello World application in Android Studio. I got the following error: Emulator: ERROR: x86 emulation ... tell me what I can do with the error? Question&Answers:os...

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

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Javascript: How to detect if browser window is scrolled to bottom?

I need to detect if a user is scrolled to the bottom of a page. If they are at the bottom of the page, ... page or if they have scrolled higher on the page? Question&Answers:os...

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

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c - 'float' vs. 'double' precision

The code float x = 3.141592653589793238; double z = 3.141592653589793238; printf("x=%f ", x); printf("z= ... ? Why don't doubles have 14 significant figures? Question&Answers:os...

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

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android - Change Volley timeout duration

I use the new Volley framework for Android to do a request to my server. But it timeouts before getting the ... way to change the timeout to a long value? Question&Answers:os...

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

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c# - Delete a file being used by another process

I'm trying to programmically delete a file, but the file is apparently being used by another process (which ... remove the file from my application's processes? Question&Answers:os...

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

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excel - Copy Paste Values only( xlPasteValues )

I'm trying to copy entire column in sheetA to Sheet B. sheetA column has values formed with formuls. I ... End With Next Application.CutCopyMode = False End Sub Question&Answers:os...

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

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r - Can lists be created that name themselves based on input object names?

It would be very helpful to me to be able to create an R list object without having to specify the names of ... 18 19 20 This would be ideal. Any suggestions? Question&Answers:os...

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

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Jsoup Java HTML parser : Executing Javascript events

Can I fill out forms, execute events and Javascript functions in Jsoup? If yes how can I? Or should I go for another parser. Question&Answers:os...

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

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php - Warning: mysqli_query() expects parameter 1 to be mysqli, null given in

I am trying to build a simple custom CMS, but I'm getting an error: Warning: mysqli_query() expects parameter 1 to be ... ['SubHeading']; echo "</div>"; } } Question&Answers:os...

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

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symbolic references - How can I use a variable as a variable name in Perl?

I need to achieve the following in perl printmsg(@val1, $msg1) if @val1; printmsg(@val2, $msg2) if @val2; printmsg ... doesn't work and breaks out with errors. Question&Answers:os...

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

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php - Fatal error: Call to undefined function session_register()

session_register("username"); // session checker for pages $_SESSION['username']= $username; // storing username in ... php5.3 how can i solve this problems Question&Answers:os...

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

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javascript - Why doesn't my equality comparison using = (a single equals) work correctly?

This question already has answers here: Question&Answers:os...

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

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android - findViewById returns null

I have code: public class HelloWorld extends Activity { private Button buttonOk; private Button buttonCancel; private ... null. What i am doing wrong? Question&Answers:os...

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

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scope - JavaScript closures vs. anonymous functions

A friend of mine and I are currently discussing what is a closure in JS and what isn't. We just ... of those two solutions uses closures to accomplish this. Question&Answers:os...

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

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encoding - What is the difference between UTF-8 and Unicode?

I have heard conflicting opinions from people - according to the Wikipedia UTF-8 page. They are the same thing, aren't they? Can someone clarify? Question&Answers:os...

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

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javascript - jQuery get specific option tag text

All right, say I have this: <select id='list'> <option value='1'>Option A</option> <option value='2'>Option B</ ... value='2']").text(); But it is not working. Question&Answers:os...

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

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time - Should MySQL have its timezone set to UTC?

Follow up question of https://serverfault.com/questions/191331/should-servers-have-their-timezone-set-to-gmt-utc Should ... UTC) What are the pros and cons? Question&Answers:os...

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

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attributes - Why use Ruby's attr_accessor, attr_reader and attr_writer?

Ruby has this handy and convenient way to share instance variables by using keys like attr_accessor :var attr_reader : ... they wouldn't have made such keys. Question&Answers:os...

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

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macos - Environment variables in Mac OS X

Update: The link below does not have a complete answer. Having to set the path or variable in two places ( ... have to restart/logout to make this take effect. Question&Answers:os...

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

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android - How do I find out which keystore was used to sign an app?

I have an app which is signed and several keystore files. I'd like to update the app, so I need to find ... app against various keystores I have on my machine? Question&Answers:os...

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

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bash - Getting ssh to execute a command in the background on target machine

This is a follow-on question to the How do you use ssh in a shell script? question. If I want to execute a ... have SSH keys set up so no password is required. Question&Answers:os...

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

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157 views

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java - How to make an Android device vibrate? with different frequency?

I wrote an Android application. Now, I want to make the device vibrate when a certain action occurs. How can I do this? Question&Answers:os...

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

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python - pandas: filter rows of DataFrame with operator chaining

Most operations in pandas can be accomplished with operator chaining (groupby, aggregate, apply, etc), but the only way I' ... (lambda x: x['column'] == value) Question&Answers:os...

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

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python - Reading a huge .csv file

I'm currently trying to read data from .csv files in Python 2.7 with up to 1 million rows, and 200 columns ... 3.40 GHz (not certain what information you need). Question&Answers:os...

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

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