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Count number of rows within each group
... standard nowadays to use .() instead of list() and setDT() to convert a data.frame to data.table. So in one step setDT(df)[, .N, by = .(year, month)].
– sindri_baldur
Sep 27 '19 at 11:33
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How do I add a Fragment to an Activity with a programmatically created content view
...tructor (with no parameters) to be public and visible. Moving the fragment into the Activity as an inner class, or creating a new java file for the fragment fixes that.
The second issue is that when you're adding a fragment this way, you must pass a reference to the fragment's containing view, and ...
Printing leading 0's in C?
...i, o, u, x, X, a, A, e,
E, f, F, g, and G conversions, the converted value is padded on
the left with zeros rather than blanks. If the 0 and - flags
both appear, the 0 flag is ignored. If a precision is given
with a numeric c...
How to work with complex numbers in C?
.../
#include <complex.h> /* Standard Library of Complex Numbers */
int main() {
double complex z1 = 1.0 + 3.0 * I;
double complex z2 = 1.0 - 4.0 * I;
printf("Working with complex numbers:\n\v");
printf("Starting values: Z1 = %.2f + %.2fi\tZ2 = %.2f %+.2fi\n", creal(z1), ci...
How do I calculate square root in Python?
...int division by default,
from __future__ import division
Or, you could convert 1 or 2 of 1/2 into a floating point value.
sqrt = x**(1.0/2)
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How does HashSet compare elements for equality?
...hat means you have two options:
Pass a custom IEqualityComparer<T> into the constructor. This is the best option if you can't modify the T itself, or if you want a non-default equality relation (e.g. "all users with a negative user ID are considered equal"). This is almost never implemented ...
ReSharper Abbreviations List: Where can I modify it?
I am using ReSharper 4.5, and what often happens when I am converting explicit properties into auto-properties, is that I will accidentally chose "Add XX to abbreviations list".
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How to programmatically take a screenshot on Android?
... FileOutputStream outputStream = new FileOutputStream(imageFile);
int quality = 100;
bitmap.compress(Bitmap.CompressFormat.JPEG, quality, outputStream);
outputStream.flush();
outputStream.close();
openScreenshot(imageFile);
} catch (Throwable e) {
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void in C# generics?
...opeful that maybe things might work like that eventually. Does your last point mean that we are not likely to ever have things work that way?
– Dave Cousineau
Jul 3 '12 at 20:56
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What is the best way to dump entire objects to a log in C#?
...rays (it just displays the type and the length of the array, but doesn't print its contents).
– Konrad Morawski
Sep 20 '12 at 6:57
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