All Questions
14 questions
2
votes
1
answer
140
views
Problem with mismatched length when using a mask
I'm writing a code and I have a function that calculates the values that are not fulfilling a condition with the values that are fulfilling the condition, but I'm having a lot of trouble with managing ...
0
votes
3
answers
76
views
python and problems with passing array to a function
I need to solve some ordinary differential equation dy/dx = f(x) = x^2 ln(x) and to proceed I create the array xpt between the limits 0. <= xpt <= 2. Because I have to be careful at xpt = 0, I ...
- 165
0
votes
1
answer
52
views
Is it possible that my python code for calculating numerical partial derivatives can be further simplified?
I want to compute the 1st-order partial derivatives of a 3D Cartesian mesh with shape (Nmesh, Nmesh, Nmesh), e.g. Nmesh=512 by the fourth-order accuracy scheme, i.e.
f'(n) = 2*(f(n+1)-f(n-1))/(3*dh) - ...
- 123
0
votes
0
answers
23
views
How to implement struct.unpack in Java with Integer type? [duplicate]
Following the similar question, I am trying to implement the unpack method in Java for Integer:
Sample byte array input: chunkByte[1219:1240] = [64, 30, 31, 0, 64, 118, 31, 0, 64, -22, 29, 0, 64, 4, ...
- 51
0
votes
0
answers
42
views
Mismatched Vector Sizes: operands could not be broadcast together with shapes (2,) (99,) - need help checking array syntax/operations
I am attempting to calculate the following five-point symmetric scheme for the diffusion equation (temperature diffusing through a rod with end points having temp = 100 degrees C).
This is the formula ...
0
votes
1
answer
58
views
How I can pass data of methods to others using oop, for example with numerical methods in python
This error appears, ValueError: setting an array element with a sequence. I did it without oop and work it nice. I need the data of def loop(self): to pass it to the def f(self, x, y): and keeping the ...
0
votes
2
answers
110
views
What is the reason for IndexError: list index out of range?
So, my professor asked me to create a program that will use the Runge-Kutta Method (2nd order) to solve the problem. But I get an IndexError: list index out of range which goes back to my first ...
2
votes
2
answers
143
views
Trying to understand syntax with index slicing in python matrix
I have been looking over and interpreting some sample code and am having some trouble understanding what is going on with a bit of slicing syntax. For some context I am working on a computational ...
- 21
2
votes
0
answers
101
views
Why is my array returning a repeated single value
I have this code which is supposed to return a list of different spatial distances. However, when I print the array, it is only a single value filled in the array which is clearly wrong. The logic ...
- 97
2
votes
2
answers
3k
views
How to calculate boundary points of numerical derivative in python?
I'm trying to write a function to take the derivative of any general function / array of numbers. Specifically, I am using a Central difference formula. The issue is, I cannot compute the boundary ...
- 7,338
1
vote
1
answer
551
views
Numpy/Python numerical instability issue multiplying large arrays
I have created a function to rotate a vector by a quaternion:
def QVrotate_toLocal(Quaternion,Vector):
#NumSamples x Quaternion[w,x,y,z]
#NumSamples x Vector[x,y,z]
#For example shape (...
0
votes
2
answers
138
views
Move from an array of 'labels' to array of equations corresponding to those labels in Python 2.7
How can I efficiently move from an array of essentially labels to equations corresponding to those labels in python 2.7?
This image illustrates what I mean:
The equations pull values from array x, so ...
2
votes
2
answers
5k
views
numpy - Sample repeatedly from matrix using np.random.choice
I have a 2D array, where each row is a direction:
directions = np.array([[ 1, 0],
[-1, 0],
[ 0, 1],
[ 0,-1]])
I want to sample ...
- 11.6k
15
votes
4
answers
12k
views
argsort for a multidimensional ndarray
I'm trying to get the indices to sort a multidimensional array by the last axis, e.g.
>>> a = np.array([[3,1,2],[8,9,2]])
And I'd like indices i such that,
>>> a[i]
array([[1, 2, 3]...
- 18.7k