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How does one reorder columns in a data frame?
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354
Your dataframe has four columns like so df[,c(1,2,3,4)].
Note the first comma means keep all the...
Remove insignificant trailing zeros from a number?
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143
If you convert it to a string it will not display any trailing zeros, which aren't stored in th...
Sending images using Http Post
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145
I'm going to assume that you know the path and filename of the image that you want to upload. A...
How can I convert tabs to spaces in every file of a directory?
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answered Jun 19 '12 at 4:35
Martin BeckettMartin Beckett
88.4k2323 gold badges175175 silver badges248248 bronze badges
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Mysql order by specific ID values
...rder by" using predefined set of column values (ID) like: order by (ID=1,5,4,3) so I would get record 1, 5, 4, 3 in that order out?
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Get a pixel from HTML Canvas?
...pixel and invert the color.
for (var i = 0, n = pix.length; i < n; i += 4) {
pix[i ] = 255 - pix[i ]; // red
pix[i+1] = 255 - pix[i+1]; // green
pix[i+2] = 255 - pix[i+2]; // blue
// i+3 is alpha (the fourth element)
}
// Draw the ImageData at the given (x,y) coordinates.
conte...
Why isn't std::initializer_list a language built-in?
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48
There were already examples of "core" language features that returned types defined in the std ...
Assigning code to a variable
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edited Apr 17 '14 at 19:38
answered Apr 16 '14 at 20:42
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__lt__ instead of __cmp__
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Alex MartelliAlex Martelli
725k148148 gold badges11261126 silver badges13241324 bronze badges
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Cartesian product of x and y array points into single array of 2D points
...mpy.transpose([numpy.tile(x, len(y)), numpy.repeat(y, len(x))])
array([[1, 4],
[2, 4],
[3, 4],
[1, 5],
[2, 5],
[3, 5]])
See Using numpy to build an array of all combinations of two arrays for a general solution for computing the Cartesian product of N arrays.
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