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Solution 1:Connect to the internet and run this command below, to fix the errorsudo apt-get install --reinstall ttf-mscorefonts-installer This will reinstall the package, and download the data files needed to configure the package. Wait for some times to finish downloading. The download size is appr 阅读全文
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NumPy has the same functionality as Matlab in terms of arrays (maybe a little more) but there are some syntax differences in creating and indexing arrays that confused me at first when switching from Matlab to NumPy.There is amore comprehensive tutorialon NumPy, here I’m just trying to work out some 阅读全文
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刚学用Python的时候,特别是看一些库的源码时,经常会看到func(*args, **kwargs)这样的函数定义,这个*和**让人有点费解。其实只要把函数参数定义搞清楚了,就不难理解了。先说说函数定义,我们都知道,下面的代码定义了一个函数funcAdef funcA(): pass显然,函数funcA没有参数(同时啥也不干:D)。下面这个函数funcB就有两个参数了,def funcB(a, b): print a print b调用的时候,我们需要使用函数名,加上圆括号扩起来的参数列表,比如 funcB(100, 99),执行结果是:10099很明显,参数的顺序和个数要和函数定义中一致, 阅读全文
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One of the questions an instrutor dreads most from a mathematically unsophisticated audience is, "What exactly is degrees of freedom?" It's not that there's no answer. The mathematical answer is a single phrase, "The rank of a quadratic form." The problem is translating t 阅读全文
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1.在类里声明的类的静态成员只是起到一个说明作用,并不会分配成员的变量空间.必须另外在类外面进行声明.例如,intBoy::m=0;即使不进行初赋值,也要有这样一个定义语句:intBoy:m;因为只有这样,编译程序才分配了变量的空间.否则,便会在链接的时候,出现:undefinedreferenceto`Boy::m'这样的错误.2.尽管成员是在类的定义体之外定义的,但成员定义就好像它们是在类的作用域中一样。回忆一下,出现在类的定义体之外的成员定义必须指明成员出现在哪个类中:doubleSales_item::avg_price()const{if(units_sold)returnr 阅读全文
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情况一:使用sqlplus登录正常输入用户名的口令,就会报错,因为SYS是在数据库之外的超级管理员,所以我们在登录的时候要在输入口令:口令+as sysdba(比如:123456 as sysdba)情况二:使用PL/SQL登录这是我们平时的登录数据库很常规的操作,但是用SYS作为用户名登录的时候就会报ORA-28009:connection as SYS should be as SYSDBA OR SYSOPER这样的错解决方法是:将“连接为”选项框的Normal改为SYSDBA或SYSOPER,即可登录成功 阅读全文
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方法一ctrl+v 进入列编辑模式,向下或向上移动光标,把需要注释的行的开头标记起来,然后按大写的I(shift+i),再插入注释符,比如"//",再按Esc,就会全部注释了批量去掉注释ctrl+v,进入列编辑模式,横向选中列的个数(如"//"注释符号,需要选中两列),然后按d, 就会删除注释符号方法二使用下面命令在指定的行首添加注释::起始行号,结束行号s/^/注释符/g取消注释::起始行号,结束行号s/^注释符//g例子:在10 - 20行添加 // 注释:10,50s#^#//#g在10 - 20行删除 // 注释:10,20s#^//##g 阅读全文
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这里从官方文档做一些整理,以备后续查看。msg的定义不用说了,这里说说msg在ros相关项目中实现的东西。1. msg overviewROS uses a simplified messages description language for describing the data values (akamessages) that ROSnodespublish. This description makes it easy for ROS tools to automatically generate source code for the message type in severa 阅读全文
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Q:Hi i am new to ROS, i have done the tutorials. But i am a bit unsure on how to read messages (in code)If i have a ros node which has subscribed to a topic /LaserScan see bellow std_msgs/Header header float32 angle_min float32 angle_max float32 angle_increment float32 time_increment float32 scan_ti 阅读全文
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Q:Suppose I have the following string:s = 'Foo 1.000 3.000 3.554'I would like to read it with the textscan function as follows.[name x y z] = textscan(s, '%s %f %f %f')However, when I do this, I always get the Too many output arguments error.I think it has to do with the fact that te 阅读全文