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Finding quaternion representing the rotation from one vector to another
I have two vectors u and v. Is there a way of finding a quaternion representing the rotation from u to v?
7 Answers
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Null vs. False vs. 0 in PHP
...m told that good developers can spot/utilize the difference between Null and False and 0 and all the other good "nothing" entities.
What is the difference, specifically in PHP? Does it have something to do with === ?
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jQuery's jquery-1.10.2.min.map is triggering a 404 (Not Found)
...get the files
Next, it's an easy fix. Head to http://jquery.com/download/ and click the Download the map file link for your version, and you'll want the uncompressed file downloaded as well.
Having the map file in place allows you do debug your minified jQuery via the original sources, which wil...
Last non-empty cell in a column
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This works with both text and numbers and doesn't care if there are blank cells, i.e., it will return the last non-blank cell.
It needs to be array-entered, meaning that you press Ctrl-Shift-Enter after you type or paste it in. The below is for colu...
Explain how finding cycle start node in cycle linked list work?
I understand that Tortoise and Hare's meeting concludes the existence of loop, but how does moving tortoise to beginning of linked list while keeping the hare at meeting place, followed by moving both one step at a time make them meet at starting point of cycle?
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Getting output of system() calls in Ruby
If I call a command using Kernel#system in Ruby, how do I get its output?
15 Answers
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How to detect if a script is being sourced
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This seems to be portable between Bash and Korn:
[[ $_ != $0 ]] && echo "Script is being sourced" || echo "Script is a subshell"
A line similar to this or an assignment like pathname="$_" (with a later test and action) must be on the first line of the s...
Linear Regression and group by in R
...ction. My data is an annual time series with one field for year (22 years) and another for state (50 states). I want to fit a regression for each state so that at the end I have a vector of lm responses. I can imagine doing for loop for each state then doing the regression inside the loop and adding...
Java's L number (long) specification
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There are specific suffixes for long (e.g. 39832L), float (e.g. 2.4f) and double (e.g. -7.832d).
If there is no suffix, and it is an integral type (e.g. 5623), it is assumed to be an int. If it is not an integral type (e.g. 3.14159), it is assumed to be a double.
In all other cases (byte, sho...
What is the result of % in Python?
...odulo operator always yields a result with the same sign as its second operand (or zero); the absolute value of the result is strictly smaller than the absolute value of the second operand [2].
Taken from http://docs.python.org/reference/expressions.html
Example 1:
6%2 evaluates to 0 because the...