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Find MongoDB records where array field is not empty
... the key, you can use:
ME.find({ pictures: { $exists: true, $not: {$size: 0} } })
MongoDB don't use indexes if $size is involved, so here is a better solution:
ME.find({ pictures: { $exists: true, $ne: [] } })
Since MongoDB 2.6 release, you can compare with the operator $gt but could lead to u...
linux下iptables配置详解 - 更多技术 - 清泛网 - 专注C/C++及内核技术
...pt source destination
Chain RH-Firewall-1-INPUT (0 references)
target prot opt source destination
ACCEPT all -- 0.0.0.0/0 0.0.0.0/0
ACCEPT icmp -- 0.0.0.0/0 0.0.0.0/0 icm...
Linear Regression and group by in R
...ual time series with one field for year (22 years) and another for state (50 states). I want to fit a regression for each state so that at the end I have a vector of lm responses. I can imagine doing for loop for each state then doing the regression inside the loop and adding the results of each reg...
How to define a two-dimensional array?
...
1039
You're technically trying to index an uninitialized array. You have to first initialize the ou...
Convert pandas dataframe to NumPy array
...
409
To convert a pandas dataframe (df) to a numpy ndarray, use this code:
df.values
array([[nan, ...
How to test valid UUID/GUID?
... first character of the third block).
Therefore to validate a UUID...
/^[0-9a-f]{8}-[0-9a-f]{4}-[0-5][0-9a-f]{3}-[089ab][0-9a-f]{3}-[0-9a-f]{12}$/i
...ensures you have a canonically formatted UUID that is Version 1 through 5 and is the appropriate Variant as per RFC4122.
NOTE: Braces { and } ar...
What's the difference between tilde(~) and caret(^) in package.json?
...
4053
See the NPM docs and semver docs:
~version “Approximately equivalent to version”, will up...
How to pretty-print a numpy.array without scientific notation and with given precision?
...o set the precision of the output:
import numpy as np
x=np.random.random(10)
print(x)
# [ 0.07837821 0.48002108 0.41274116 0.82993414 0.77610352 0.1023732
# 0.51303098 0.4617183 0.33487207 0.71162095]
np.set_printoptions(precision=3)
print(x)
# [ 0.078 0.48 0.413 0.83 0.776 0.102...
How to make an OpenGL rendering context with transparent background?
...ndows XP (32-bits) and Windows 8.1 (32-bits).
Enjoy!
#define _WIN32_WINNT 0x0500
#include <windows.h>
#include <windowsx.h>
#include <GL/gl.h>
#include <GL/glu.h>
#pragma comment (lib, "opengl32.lib")
#pragma comment (lib, "glu32.lib")
#include <assert.h>
#include &...
Are +0 and -0 the same?
Reading through the ECMAScript 5.1 specification , +0 and -0 are distinguished.
9 Answers
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