What are the advantages of NumPy over regular Python lists?

What are the advantages of NumPy over regular Python lists? I have approximately 100 financial markets series, and I am going to create a cube array of 100x100x100 = 1 million cells. I will be...

Adobe Photoshop-style posterization and OpenCV

It seems Adobe Photoshop does posterization by quantizing each color channel separately, based on the number of levels specified. So for example, if you specify 2 levels, then it will take the R...

How to create a numpy array of all True or all False?

In Python, how do I create a numpy array of arbitrary shape filled with all True or all False?

Most memory-efficient way to compute abs()**2 of complex numpy ndarray

I'm looking for the most memory-efficient way to compute the absolute squared value of a complex numpy ndarray arr = np.empty((250000, 150), dtype='complex128') # common size I haven't found a...

affinity propagation in python

I am seeing something strange while using AffinityPropagation from sklearn. I have a 4 x 4 numpy ndarray - which is basically the affinity-scores. sim[i, j] has the affinity score of [i, j]. Now,...

What is the purpose of meshgrid in Python / NumPy?

Can someone explain to me what is the purpose of meshgrid function in Numpy? I know it creates some kind of grid of coordinates for plotting, but I can't really see the direct benefit of it. I am...

Numpy ndarray object with string and floating point number types in it

I have a file text with data in a following format: rubbish & 3.97& 3.83& 3.95& 3.83& 3.82 rubbish & 4.92& 4.81& 4.88& 4.81& 4.81 rubbish & 5.90& 5.66& 5.88& 5.66& 5.66 rubbish &--- & 6.05& 6.14&...

CSV >> Tensorflow >> regression (via neural network) model

TLDR; 1) read and convert CSV data to image, 2) create regression model from data. Note that I was very new to python, deep learning, and Stackoverflow in 2016. Please vote to close this. I think...

Increasing performance of highly repeated numpy array index operations

In my program code I've got numpy value arrays and numpy index arrays. Both are preallocated and predefined during program initialization. Each part of the program has one array values on which...

Python 3 - FileNotFoundError: [Errno 2] No such file or directory: '../data/mnist.pkl'

I'm trying to load the mnist data set for this neural networks and deep learning example (http://neuralnetworksanddeeplearning.com/chap1.html) but I keep getting this error. >>> import...

Covert Python Http request to Java

I want to convert following Python code snippet of Http request to equivalent Java code, import requests from requests.auth import HTTPBasicAuth from numpy import array try: from commands...

Build confusion matrix from two vector

I need to define a function that generates a confusion matrix. So I have two vectors, y_label and y_predict, the element values of which are either 0, 1, 2. The goal of the function is to create a...

How to give float indexes to numpy ndarray?

In a time series data, I have (x,y) coordinates for an object that evolve over a 2-D grid. For example: (41.797, 34.0), (42.152, 34.56), (42.383, 36.07), (42.505, 37.97) How do I index the array...

finding peak values and corresponding timestamps

I'm trying to use scipy to identify peaks of my signals and try to get the corresponding timestamps of those peaks. Used scipy.signal.find_peaks...

Unable to plot scatter plot because of TypeError

I have a dataset, in which i will be using only a single column to apply kmeans clustering. However while plotting the graph, i am getting "numpy.ndarray". I tried converting to float, but still...

Solar Zenith Angle for many coordinates using PVLIB

I need calculate the solar zenith angle for approximately 106.000.000 of different coordinates. This coordinates are referrals to the pixels from an image projected at Earth Surface after the...

fill vector values between specified indices

Starting from a vector a and a list ind of indices, I want to set the elements of a corresponding to indices in ind as a function of the original vector (in the example I will just add 10 to the...

How to read numpy array in ND4j

I have too components that deal with n-dimension array. One component is written in python which process the data and save the processed ndarray by tobytes(). Now the other component is written in...

ValueError: Dimensions of labels and X must be compatible

After running the code, this happens: ValueError: Dimensions of labels and X must be compatible I do not quite understand what is the error above Honestly, pretty new to python, was referring to...

Why is numpy's arange displayed with precision errors in PyCharm?

I am using PyCharm Professional with Python 3.7.4 64bit. When I am evaluating the result of np.arange(2, 4, 0.01) it is displayed with precision erros (see image). np.array([x / 100 for x in...

(Keras) ValueError: Failed to convert a NumPy array to a Tensor (Unsupported object type float)

I know this problem has been answered previously in the link below,but it does not apply to my...

Find Nearest Transition in N-dimensional Array

I want to find index of the nearest transition in a numpy ndarray of integers given a current index in an efficient manner. Transition means a change of value. For example, in the 2D array below,...

scipy matrix solver error: nzvals is not of a type supported by SuperLU

I'm trying to use the script from an answered question that uses scipy matrix solver to fit a baseline to some spectral data, by solving a matrix equation of the type: Ax=b. Here's a section of my...

Trouble with PyTorch's 'ToPILImage'

Why does this not work? import torchvision.transforms.functional as tf from torchvision import transforms pic = np.random.randint(0, 255+1, size=28*28).reshape(28, 28) pic =...

2Dimentional Numpy array(NDarray) to C#: Linq Query returns limitations of Marshal.Copy error

I have implemented a ML model using keras in c#. The output is a 4dim vector. I have the following predict function to predict one entry. public (DateTime TimeStamp, double dim1, double dim2,...

Select multiple rows multiple times from a numpy array at once avoiding loops

I am looking for a way to select multiple rows from a numpy array multiple times given an array of indexes. Given M and indexes, I would like to get N avoiding for loop, since it is slow for big...

What does arr[:,[1,0,2] means in the snippet of code?

I was doing numpy, and this is how they were swapping columns 1 and 2 in an array. arr[:, [1,0,2]] Here, what does [1,0,2] means?

"Can only read from Matlab level 5 MAT-files"

I'm trying to load a file from Matlab into my python using mat4py. I had the following error ParseError: Unexpected field name length: 43 when using import h5py from numpy import...

PySimpleGUI/tk: drawing OpenCV image into sg.Graph efficiently

An image captured from a camera is stored into a numpy ndarray object with a shape of (1224,1024,3). This format is very convenient for using OpenCV methods over it. I was looking for the way to...

module 'numpy' has no attribute 'ndarray'

I really appreciate your help! My Jupiter notebook was crushed, so I have to reinstall the notebook, but in the new Jupiter notebook, I cannot run pandas. import pandas as pd AttributeError ...