Splitting a string into separate variables
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Extracting value specific rows in R
Assuming that your data is in a data frame called mydata, you can select the rows you want by writing It might be easier to understand by doing it in multiple steps:
“Notice: Undefined variable”, “Notice: Undefined index”, and “Notice: Undefined offset” using PHP
Notice: Undefined variable From the vast wisdom of the PHP Manual: Relying on the default value of an uninitialized variable is problematic in the case of including one file into another which uses the same variable name. It is also a major security risk with register_globals turned on. E_NOTICE level error is issued in case of working with uninitialized variables, however not … Read more
Multi-line string with extra space (preserved indentation)
Heredoc sounds more convenient for this purpose. It is used to send multiple commands to a command interpreter program like ex or cat The string after << indicates where to stop. To send these lines to a file, use: You could also store these lines to a variable: This stores the lines to the variable named VAR. When printing, remember the … Read more
How do I concatenate two lists in Python?
You can use the + operator to combine them: Output:
How to read a local text file?
You need to check for status 0 (as when loading files locally with XMLHttpRequest, you don’t get a status returned because it’s not from a Webserver) And specify file:// in your filename:
C# compiler error: “not all code paths return a value”
You’re missing a return statement. When the compiler looks at your code, it’s sees a third path (the else you didn’t code for) that could occur but doesn’t return a value. Hence not all code paths return a value. For my suggested fix, I put a return after your loop ends. The other obvious spot – adding an else that had a return value to the if-else-if – … Read more
XPath contains(text(),’some string’) doesn’t work when used with node with more than one Text subnode
The <Comment> tag contains two text nodes and two <br> nodes as children. Your xpath expression was To break this down, * is a selector that matches any element (i.e. tag) — it returns a node-set. The [] are a conditional that operates on each individual node in that node set. It matches if any of the individual nodes it operates on … Read more
How is “mvn clean install” different from “mvn install”?
clean is its own build lifecycle phase (which can be thought of as an action or task) in Maven. mvn clean install tells Maven to do the clean phase in each module before running the install phase for each module. What this does is clear any compiled files you have, making sure that you’re really compiling each module from scratch.