mean

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 由 翻译 强力驱动 问题: I am currently getting the error, java . sql . SQLException : Method 'executeQuery(String)' not allowed on prepared statement . because I am using PreparedStatement stmt = conn . prepareStatement ( sql ); and also had ResultSet rs = stmt . executeQuery ( sql ); in my code. I now need to remove the ResultSet line but that leaves me with having to deal with the following code: if ( rs . next ()) { messages . add ( ActionMessages . GLOBAL_MESSAGE , new ActionMessage ( "login.successful" )); request . getSession ( true ). setAttribute

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: I'm studying the content of this preinst file that the script executes before that package is unpacked from its Debian archive (.deb) file. The script has the following code: #!/bin/bash set -e # Automatically added by dh_installinit if [ "$1" = install ]; then if [ -d /usr/share/MyApplicationName ]; then echo "MyApplicationName is just installed" return 1 fi rm -Rf $HOME/.config/nautilus-actions/nautilus-actions.conf rm -Rf $HOME/.local/share/file-manager/actions/* fi # End automatically added section My first query is about the line: set

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: numpy.average() has a weights option, but numpy.std() does not. Does anyone have suggestions for a workaround? 回答1: How about the following short "manual calculation"? def weighted_avg_and_std(values, weights): """ Return the weighted average and standard deviation. values, weights -- Numpy ndarrays with the same shape. """ average = numpy.average(values, weights=weights) # Fast and numerically precise: variance = numpy.average((values-average)**2, weights=weights) return (average, math.sqrt(variance)) 回答2: There is a class in statsmodels to

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: I'm trying to use in Python 3.3 an old library (dating from 2003!). When I import it, Python throws me an error because there are <> signs in the source file, e.g.: if (cnum < 1000 and nnum <> 1000 and ntext[-1] <> "s": ... I guess it's a now-abandoned sign in the language. What exactly does it mean, and which (more recent) sign should I replace it with? 回答1: It means not equal to. It was taken from ABC (python's predecessor) see here : x < y, x <= y, x >= y, x > y, x = y, x <> y, 0 <= d < 10 Order tests ( <> means 'not equals' ) I believe

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: What does .class mean in Java? For example, if I created a class called Print . What does Print.class return? 回答1: When you write .class after a class name, it references the class literal - java.lang.Class object that represents information about given class. For example, if your class is Print , then Print.class is an object that represents the class Print on runtime. It is the same object that is returned by the getClass() method of any (direct) instance of Print . Print myPrint = new Print(); System.out.println(Print.class.getName());

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: How can I convert a uniform distribution (as most random number generators produce, e.g. between 0.0 and 1.0) into a normal distribution? What if I want a mean and standard deviation of my choosing? 回答1: The Ziggurat algorithm is pretty efficient for this, although the Box-Muller transform is easier to implement from scratch (and not crazy slow). 回答2: There are plenty of methods: Do not use Box Muller. Especially if you draw many gaussian numbers. Box Muller yields a result which is clamped between -6 and 6 (assuming double precision. Things

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: I saw this here and I don't know what it means: &(int) { 1 } I thought it was weird because it seems like invalid syntax. It's casting a block scope(?) with a random 1 in the middle (without a semi-colon) and taking the address. Doesn't make a lot of sense to me. Could you guys enlighten me? Tried it out w/ C++11, so it compiles: auto a = &(int) { 1 }; But I have no idea what to do with the variable. 回答1: As far as I can tell this is a compound literal , it is C99 feature, it is not standard C++ but both gcc and clang support it as an

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: I have a data frame like this which is imported from a CSV. stock pop Date 2016-01-04 325.316 82 2016-01-11 320.036 83 2016-01-18 299.169 79 2016-01-25 296.579 84 2016-02-01 295.334 82 2016-02-08 309.777 81 2016-02-15 317.397 75 2016-02-22 328.005 80 2016-02-29 315.504 81 2016-03-07 328.802 81 2016-03-14 339.559 86 2016-03-21 352.160 82 2016-03-28 348.773 84 2016-04-04 346.482 83 2016-04-11 346.980 80 2016-04-18 357.140 75 2016-04-25 357.439 77 2016-05-02 356.443 78 2016-05-09 365.158 78 2016-05-16 352.160 72 2016-05-23 344.540 74 2016-05-30

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 由 翻译 强力驱动 问题: I posted a similar question on how scalable linq is. There were so many different views on what scalability actually meant in some recent conversations, so it has sparked me to ask this question as well. What does scalability mean to you? 回答1: I look at scalability from two perspectives: Scaling Up If I add more RAM to the box that something is running on, how much additional performance and capacity do I gain? If one application I have can handle 300 more connections and runs 15% faster when I add 2 GB of RAM to my server and

前言 这个函数的功能比较强大，它首先将数据进行分组（按行），然后对每一组数据进行函数统计，最后把结果组合成一个比较nice的表格返回。根据数据对象不同它有三种用法，分别应用于数据框（data.frame）、公式（formula）和时间序列（ts）： aggregate(x, by, FUN, ..., simplify = TRUE) aggregate(formula, data, FUN, ..., subset, na.action = na.omit) aggregate(x, nfrequency = 1, FUN = sum, ndeltat = 1, ts.eps = getOption("ts.eps"), ...) 语法 aggregate(x, ...) ## S3 method for class 'default': aggregate((x, ...)) ## S3 method for class 'data.frame': aggregate((x, by, FUN, ..., simplify = TRUE)) ## S3 method for class 'formula': aggregate((formula, data, FUN, ..., subset, na.action = na.omit)) ## S3 method for