大约有 37,000 项符合查询结果（耗时：0.0467秒） [XML]
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 $gt but could lead to u...
Linear Regression and group by in R
...ual time series with one field for year (22 years) and another for state (50 states). I want to fit a regression for each state so that at the end I have a vector of lm responses. I can imagine doing for loop for each state then doing the regression inside the loop and adding the results of each reg...
How to define a two-dimensional array?
...
1039
You're technically trying to index an uninitialized array. You have to first initialize the ou...
Convert pandas dataframe to NumPy array
...
409
To convert a pandas dataframe (df) to a numpy ndarray, use this code:
df.values
array([[nan, ...
How to test valid UUID/GUID?
... first character of the third block).
Therefore to validate a UUID...
/^[0-9a-f]{8}-[0-9a-f]{4}-[0-5][0-9a-f]{3}-[089ab][0-9a-f]{3}-[0-9a-f]{12}$/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
...
Bomb dropping algorithm
...the only way to reduce the hollow rectangle of squares on the
perimeter to 0 is to bomb either the perimeter or to bomb the hollow rectangle of
squares just inside the perimeter. I'll call the perimeter layer 1, and the rectangle inside it layer 2.
An important insight is that there is no point b...