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How to convert a boolean array to an int array
I use Scilab, and want to convert an array of booleans into an array of integers:
6 Answers
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How to drop columns by name in a data frame
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You should use either indexing or the subset function. For example :
R> df <- data.frame(x=1:5, y=2:6, z=3:7, u=4:8)
R> df
x y z u
1 1 2 3 4
2 2 3 4 5
3 3 4 5 6
4 4 5 6 7
5 5 6 7 8
Then you can use the which fun...
Java 8: Where is TriFunction (and kin) in java.util.function? Or what is the alternative?
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As far as I know, there are only two kinds of functions, destructive and constructive.
While constructive function, as the name implies, constructs something, a destructive one destroys something, but not in the way you may think now.
For example, the fu...
How can I determine whether a 2D Point is within a Polygon?
I'm trying to create a fast 2D point inside polygon algorithm, for use in hit-testing (e.g. Polygon.contains(p:Point) ). Suggestions for effective techniques would be appreciated.
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Converting string to Date and DateTime
If I have a PHP string in the format of mm-dd-YYYY (for example, 10-16-2003), how do I properly convert that to a Date and then a DateTime in the format of YYYY-mm-dd ? The only reason I ask for both Date and DateTime is because I need one in one spot, and the other in a different spot.
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Get yesterday's date in bash on Linux, DST-safe
I have a shell script that runs on Linux and uses this call to get yesterday's date in YYYY-MM-DD format:
10 Answers
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Drawing a dot on HTML5 canvas [duplicate]
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For performance reasons, don't draw a circle if you can avoid it. Just draw a rectangle with a width and height of one:
ctx.fillRect(10,10,1,1); // fill in the pixel at (10,10)
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How do I calculate the normal vector of a line segment?
Suppose I have a line segment going from (x1,y1) to (x2,y2). How do I calculate the normal vector perpendicular to the line?
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How to map atan2() to degrees 0-360
atan2(y, x) has that discontinuity at 180° where it switches to -180°..0° going clockwise.
15 Answers
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Difference between fold and reduce?
Trying to learn F# but got confused when trying to distinguish between fold and reduce . Fold seems to do the same thing but takes an extra parameter. Is there a legitimate reason for these two functions to exist or they are there to accommodate people with different backgrounds? (E.g.: String ...