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Convert pandas dataframe to NumPy array
...
409
To convert a pandas dataframe (df) to a numpy ndarray, use this code:
df.values
array([[nan, ...
Why does changing 0.1f to 0 slow down performance by 10x?
...rap and resolve them using microcode.
If you print out the numbers after 10,000 iterations, you will see that they have converged to different values depending on whether 0 or 0.1 is used.
Here's the test code compiled on x64:
int main() {
double start = omp_get_wtime();
const float x[1...
How to add an extra column to a NumPy array
...lution and faster to boot is to do the following:
import numpy as np
N = 10
a = np.random.rand(N,N)
b = np.zeros((N,N+1))
b[:,:-1] = a
And timings:
In [23]: N = 10
In [24]: a = np.random.rand(N,N)
In [25]: %timeit b = np.hstack((a,np.zeros((a.shape[0],1))))
10000 loops, best of 3: 19.6 us per ...
How to select rows with one or more nulls from a pandas DataFrame without listing columns explicitly
I have a dataframe with ~300K rows and ~40 columns.
I want to find out if any rows contain null values - and put these 'null'-rows into a separate dataframe so that I could explore them easily.
...
Looping in a spiral
...
Here's my solution (in Python):
def spiral(X, Y):
x = y = 0
dx = 0
dy = -1
for i in range(max(X, Y)**2):
if (-X/2 < x <= X/2) and (-Y/2 < y <= Y/2):
print (x, y)
# DO STUFF...
if x == y or (x < 0 and x == -y) or (x &...
How do you detect where two line segments intersect? [closed]
...th s, getting
(p + t r) × s = (q + u s) × s
And since s × s = 0, this means
t (r × s) = (q − p) × s
And therefore, solving for t:
t = (q − p) × s / (r × s)
In the same way, we can solve for u:
(p + t r) × r = (q + u s) × r
u (s × r) = (p − q) × r
...
MDI CDockablePane使用总结 - C/C++ - 清泛网 - 专注C/C++及内核技术
...rToolBarId, uiLastUserToolBarId);
EnablePaneMenu(TRUE, ID_VIEW_CUSTOMIZE, 0, ID_VIEW_TOOLBAR);
CDockingManager::SetDockingMode(DT_SMART);
EnableAutoHidePanes(CBRS_ALIGN_ANY);
EnableDocking(CBRS_ALIGN_ANY);
（1） 第一种情况
if (!m_Panes[0].Create(_T("Pane 0"), this, CRe...
Fast permutation -> number -> permutation mapping algorithms
...ake of an example, let's say, 7 elements, 1234567. I know there are 7! = 5040 permutations possible of these 7 elements.
1...
What's the fastest way to merge/join data.frames in R?
...he first example sqldf is 3x slower than data.table and in the second its 200x faster than plyr and 100 times faster than data.table. Below we show the input code, the output timings for the merge and the output timings for the aggregate. Its also worthwhile noting that sqldf is based on a databa...
How to drop rows of Pandas DataFrame whose value in a certain column is NaN
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AMC
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answered Nov 16 '12 at 9:34
eumiroeumiro
1...