I am having a problem splicing together two arrays. Let’s assume I have two arrays: When I do vstack((a,b)) I get and if I do hstack((a,b)) I get: But what I really want is: How do I accomplish this without using for loops (it needs to be fast)? Answer column_stack.
Tag: numpy
Numpy and line intersections
How would I use numpy to calculate the intersection between two line segments? In the code I have segment1 = ((x1,y1),(x2,y2)) and segment2 = ((x1,y1),(x2,y2)). Note segment1 does not equal segment2. So in my code I’ve also been calculating the slope and y-intercept, it would be nice if that could be av…
How find values in an array that meet two conditions using Python
I have an array and I want to find the indices of the element s that meet two conditions i.e. I can use numpy.nonzero(a>3) or numpy.nonzero(a<8) but not numpy.nonzero(a>3 and a<8) which gives the error: When I try to use any or all I get the same error. Is it possible to combine two conditional te…
Weighted standard deviation in NumPy
numpy.average() has a weights option, but numpy.std() does not. Does anyone have suggestions for a workaround? Answer How about the following short “manual calculation”?
How do I calculate percentiles with python/numpy?
Is there a convenient way to calculate percentiles for a sequence or single-dimensional numpy array? I am looking for something similar to Excel’s percentile function. I looked in NumPy’s statistics reference, and couldn’t find this. All I could find is the median (50th percentile), but not …
Matplotlib runs out of memory when plotting in a loop
I have a fairly simple plotting routine that looks like this: When I plot this in single iterations, it works fine. However, the moment I put it in a loop, matplotlib throws a hissy fit… This happens on iteration 2 (counting from 1), if that makes a difference. The code is running on Windows XP 32-bit w…
Convert NumPy array to Python list
How do I convert a NumPy array into a Python List? Answer Use tolist(): Note that this converts the values from whatever numpy type they may have (e.g. np.int32 or np.float32) to the “nearest compatible Python type” (in a list). If you want to preserve the numpy data types, you could call list() o…
The Assignment Problem, a NumPy function?
Since an assignment problem can be posed in the form of a single matrix, I am wondering if NumPy has a function to solve such a matrix. So far I have found none. Maybe one of you guys know if NumPy/SciPy has an assignment-problem-solve function? Edit: In the meanwhile I have found a Python (not NumPy/SciPy) i…
Can’t import Numpy in Python
I’m trying to write some code that uses Numpy. However, I can’t import it: I tried the suggestions in this question: and I searched for files named numpy in that path: But nothing came up. So… Are there any other places in which Python modules are commonly installed? How can I install numpy …