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How do I find a “gap” in running counter with SQL?
...gap" in a counter column in an SQL table. For example, if there are values 1,2,4 and 5 I'd like to find out 3.
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Why do Lua arrays(tables) start at 1 instead of 0?
...ionale behind the decision of this part of Lua. Why does indexing start at 1? I have read (as many others did) this great paper . It seems to me a strange corner of a language that is very pleasant to learn and program. Don't get me wrong, Lua is just great but there has to be an explanation somewh...
C++常用排序算法汇总 - C/C++ - 清泛网 - 专注C/C++及内核技术
...堆排序(HeapSort)，插入排序(InsertSort)，希尔排序(ShellSort) 1、选择排序(SelectSort)
/************************************
* 简单选择排序
* 稳定排序，O{n^2} ~ O{n^2}
* 从首位开始，循环一次找出一个比首位小的值，交换
*
* https://www.tsi...
How can I setup & run PhantomJS on Ubuntu?
...ntomJS and recorded it to video: https://www.dailymotion.com/video/xnizmh_1_webcam
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Can dplyr package be used for conditional mutating?
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Use ifelse
df %>%
mutate(g = ifelse(a == 2 | a == 5 | a == 7 | (a == 1 & b == 4), 2,
ifelse(a == 0 | a == 1 | a == 4 | a == 3 | c == 4, 3, NA)))
Added - if_else: Note that in dplyr 0.5 there is an if_else function defined so an alternative would be to replace ifelse with i...
Dynamically select data frame columns using $ and a character value
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You can't do that kind of subsetting with $. In the source code (R/src/main/subset.c) it state...
How to show all shared libraries used by executables in Linux?
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How to assign from a function which returns more than one value?
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How do I represent a hextile/hex grid in memory?
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Amit Patel has posted an amazing page on this topic. It's so comprehensive and wonderful that ...
Convert RGB to RGBA over white
I have a hex color, e.g. #F4F8FB (or rgb(244, 248, 251) ) that I want converted into an as-transparent-as-possible rgba color (when displayed over white). Make sense? I'm looking for an algorithm, or at least idea of an algorithm for how to do so.
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