We may use two lists to store the values of two properties of a list of elements in Python. Under such data structure arrangement, when we need to sort the properties from one list, we may want to also make sure the other list will be also re-ordered following the same order as the first
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Category: Programming
Tutorials and tips on programming related to Linux systems, Web and more.
Reading JSON from URL in R
Posted onR is good at analyzing data. Many data are provided as JSON from RESTful APIs with an URL. R natively support many data format. For JSON, we can use some libraries. For reading JSON from URL, we can use the “jsonlite” package. In this example, we use an example of fetching BTC prices of last
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Reading Excel xls/xlsx Files in R
Posted onMany useful data are stored in Excel xls or xlsx format files. R is good at doing analysis on top of data. We would then need to import the data to R by reading the xls/xlsx files to be R data frames. In this post, we check how to import data from Excel files to
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Converting Hex to ASCII Using xxd
Posted onStrings are commonly encoded as hexadecimal (hex) strings for various purposes. Hence, it is also common to convert hex strings to its original strings such as an ASCII string. Hex to ASCII string conversion can be done programmatically in many languages. In command line, we can use xxd to convert hex to ASCII string. This
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Generating RSA Private and Public Key Pair in Go Lang?
Posted onHow to generate a pair of RSA private and public key in Go lang? Go lang has a rich set of standard libraries. Using Go’s standard libraries, we can generate RSA private and Public keys. The Crypto standard libraries in Go lang Go lang standard libraries has a rich set of cryptography functions. Here are
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2 Ways of Resetting All Git Submodules in a Git Repository
Posted onGit submodule is a nice and convenient mechanism in Git to include the other Git repositories and manage the version/commit used from the submodule Git repository. However, there are cases where we would like “reset” the submodule, such as when we find updating a submodule repository will break the code tree, or merge some updates
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Converting Int to String in C++
Posted onIt is common to convert an integer (int) to a string (std::string) in C++ programs. Because of the long history of C++ which has several versions with extended libraries and supports almost all C standard library functions, there are many ways to convert an int to string in C++. This post introduces how to convert
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Installing R and RStudio Desktop in Ubuntu Linux 20.04
Posted onWe ever discussed How To Install R and RStudio Server in Ubuntu Linux 20.04. If the purpose is to install a local RStudio IDE instead of a remote RStudio Server, we can install RStudio Desktop. In this post, we introduce how to install R and RStudio Desktop on Ubuntu Linux 20.04. For other Ubuntu version,
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Installing R and RStudio Server in Ubuntu Linux 20.04
Posted onR is a language and environment for statistical computing and graphics, providing a wide variety of statistical and graphical techniques. The R environment is open source software under GPL. R has rich software packages and is widely used for statistical analysis. RStudio Server is an R integrated development environment (IDE) that provides many useful features
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Linux Kernel: fs: handle SEEK_HOLE/SEEK_DATA properly in all fs’s that define their own llseek
Posted onThis change “fs: handle SEEK_HOLE/SEEK_DATA properly in all fs’s that define their own llseek” (commit 06222e4) in Linux kernel is authored by Josef Bacik <josef [at] redhat.com> on Mon Jul 18 13:21:38 2011 -0400. Description of “fs: handle SEEK_HOLE/SEEK_DATA properly in all fs’s that define their own llseek” The change “fs: handle SEEK_HOLE/SEEK_DATA properly in
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How to Count the Number of Words in a File in PHP?
Posted onCounting the number of words in a file is useful in many programs. In this post, we will discuss how to count the number of words in a file in a PHP script. In PHP standard library, we have function str_word_count($str) which returns the number of words from a string $str. On the other hand,
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4 Features of Python 3.9 That You Can’t Take Your Eyes Off
Posted onPython is one of the most popular programming languages in the world. It is widely popular for a plethora of tasks due to its flexible nature and ease of use. Python has also managed to beat other programming languages such as Java, which were once upon a time, the world’s favorite. In fact, the extent
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Add Inline Comments for Multi-line Command in Bash Script
Posted onIn Bash script, it is common that multiple small commands run together connected by pipes (|) and the whole command is quite long. For clarity, we may write the command in multiple lines. How to add comments for these long multi-line commands? In Bash, the content after # in a line is the comment. Using
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How to Match Multiple Lines using Regex in Perl One-liners
Posted onPerl one-liners with perl’s regular expression statement can be a very powerful text processing tools used as commands in a terminal or a script. By default, the input to the perl one-liner with -p or -n options is passed line by line. However, when we want to match multiple lines, it gets us some trouble.
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How to Install Go 1.13.x on Ubuntu 18.04
Posted onIn Ubuntu 18.04 LTS, the default Go lang version is 1.10. For compatibility reason, the Ubuntu LTS will usually keep the major release version numbers for packages. However, many applications, such as Hyperledger Fabric 2.0, require a newer version of Go. In this post, let’s take a look at how to install a system level
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GCC May “Save” You Some Recursive Functions Calls: an Analysis of a Function Call Stack Length Example
Posted onWe know compilers like gcc can do lots smart optimization to make the program run faster. Regarding functions call optimization, gcc can do tail-call elimination to save the cost of allocating a new stack frame, and tail recursion elimination to turn a recursive function to non-recursive iterative one. gcc can even transform some recursive functions
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Dynamics 365 Developer Extension is Now Working in Visual Studio 2017
Posted onI don’t know why Jason Lattimer’s D365DeveloperExensions no more working after VS 2017 release? It seems D365DeveloperExtensions anymore supported for newer Visual Studio version. I am pretty much sure, some of you may be still struggling with installing Dynamics 355 Developer extension for your Visual Studio 2017 community or professional edition. Not sure why this tool has been
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Bash Learning Materials
Posted onBash (GNU Bourne-Again SHell) the default shell for many Linux distributions. It is very common for scripting languages in Linux. Bash is easy and straightforward for writing small tools. However, as most tools, it has its grammars that could easily cause bugs if they are not used correctly. Here I summarize a list of good
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A StoneWall Solution in C++
Posted onStoneWall is an interesting problem that requires some brain cycles yet not too complex. It is good software engineer interview question. Here is a C++ solution whose complexity is O(N). #include <stack> int solution(std::vector<int> &H) { int stones = 0; std::stack<int> heights; for (auto h: H) { while (!heights.empty() && h < heights.top()) { heights.pop();
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How to Statically Link OCaml Programs
Posted onStatic linking is preferred for some cases although it has its own various problems. Static building/linking is not always possible for some languages on some platform. For OCaml, the answer to this question is yes. In this post, we will introduce 2 methods to statically linking OCaml: static linking with runtime glibc required and static
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