questions related to numpy indexing routines, in particular, slicing, indexing and concatenation
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Questions tagged [numpy-slicing]
518 questions
1
vote
2 answers
Script to convert Matlab slices and index to numpy array notation
I am porting some Matlab code to Python. In this code there are many instances of a large matrix being sliced in many different ways, eg M(2:45,13:18), M(:12,:), V(4), V(:27), etc. It is technically possible to convert this to numpy notation…
Mathieu
- 241
- 1
- 8
1
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2 answers
How to retrieve elements from an array without slicing?
Say I have an array, A1. B1 is another array storing the last two rows of A1. I need to retrieve the first two rows of A1 without slicing as another array (C1). Logically, I'm thinking something like A1 (the whole array) - B1 (the last two rows) =…
wowzer
- 25
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1
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1 answer
how to highlight pandas data frame on selected rows
I have the data like this:
df:
A-A A-B A-C A-D A-E
Tg 0.37 10.24 5.02 0.63 20.30
USL 0.39 10.26 5.04 0.65 20.32
LSL 0.35 10.22 5.00 0.63 20.28
1 0.35 10.23 5.05 0.65 20.45
2 …
A.E
- 997
- 1
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1
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0 answers
Can't convert FITS data (FITS_rec type) to multidimensional numpy array
I am attempting to read in a FITS file and convert the data into a multidimensional numpy array (So i can easily index the data).
The FITS data is structured like:
FITS_rec([(time, [rate, rate, rate, rate], [ERROR, ERROR, ERROR, ERROR], TOTCOUNTS,…
Maxwell A. Fine
- 11
- 1
1
vote
2 answers
Take only part of matrix in Python
given a matrix A, e.g. A = np.array([[1,2,3,4],[5,6,7,8]]) and two lists one of row indices and one of column indices, e.g. row=(0,1), column=(0,2) I want to extract the corresponding rows and columns of matrix A in python, so in this example I want…
samabu
- 181
- 6
1
vote
3 answers
array copy and view in numpy python
I am new to numpy.Recently only I started learning.I am doing one practice problem and getting error.
Question is to replace all even elements in the array by -1.
import numpy as np
np.random.seed(123)
array6 =…
Aakash Patel
- 111
- 7
1
vote
1 answer
How to get the specific out put for Numpy array slicing?
x is an array of shape(n_dim,n_row,n_col) of 1st n natural numbers
b is boolean array of shape(2,) having elements True,false
def array_slice(n,n_dim,n_row,n_col):
x = np.arange(0,n).reshape(n_dim,n_row,n_col)
b =…
Chandler
- 15
- 3
1
vote
3 answers
How can I get a numpy array slides by choosing with specific rows and columns inplace?
As in the title, if I have a matrix a
a = np.diag(np.arange(5))
array([[0, 0, 0, 0, 0],
[0, 1, 0, 0, 0],
[0, 0, 2, 0, 0],
[0, 0, 0, 3, 0],
[0, 0, 0, 0, 4]])
How can I assign a new 4x4 matrix or even 3x4 matrix to a…
Archibald Chain
- 59
- 4
1
vote
2 answers
Make a numpy array selecting only certain rows and certain columns from another
I have created a very large NumPy array of size 500 x 10000, called first_array, to solve a partial differential equation using the Crank Nicolson method. This method needs to create and use all the data stored in the array, but I only need a small…
User1234321
- 321
- 1
- 10
1
vote
2 answers
Value Assignment by specific indices error in Tensorflow
I'm trying to build a custom loss function for my model, but whenever I try to convert Tensors into .numpy() arrays with run_eagerly = True, it gives "WARNING: Gradients do not exist for variables ...". So I debugged other custom loss functions…
1
vote
0 answers
Delete rows and column from a numpy array, given information to delete is in another vector array
I have the following code:
deleterowandcolumns = np.array([0,3])
original = np.array ([
[1, 2, 3, 4],
[5, 6, 7, 8],
[9, 10, 11, 12],
[13, 14, 15, 16]
])
The rows and columns to…
django
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1
vote
2 answers
Slicing multi-dimensional array with another array
edited with a clearer example, and included solution
I'd like to slice an arbitrary dimensional array, where I pin the first n dimensions and keep the remaining dimensions. In addition, I'd like to be able to store the n pinning dimensions in a…
Steve Heim
- 799
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1
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1 answer
update 3D Numpy array with np.array as indices
I have a an image of the shape (180, 240, 3) and it will be modified according to 3 different numpy arrays that contains the location of each dimension.
So the three numpy arrays looks like this:
height_array = [
90 148 161 165 40 77 73 108 167…
vsun92
- 11
- 2
1
vote
1 answer
Adding a smaller array to a larger array at a specified location (using variables)
Suppose I have a 6x6 matrix I want to add into a 9v9 matrix, but I also want to add it at a specified location and not necessarily in a 6x6 block.
The below code summarizes what I want to accomplish, the only difference is that I want to use…
Ned Taylor
- 11
- 3
1
vote
2 answers
python slicing [:-N] [:-N+1]
I been trying to code the following line but I get the message that operands could not be broadcast together with shapes (0,) (30,)
x has a length of 32
x[:-N+1] I want to access all elements except the last two
x[N:-N] I want to access all…
Brucee
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