# Questions tagged [numpy]

32264 questions

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### Hamming Window, python 2.7

Hi I have a FFT which is quite noisy. How to apply to my code Hamming window to make it less noisy. Look at my code: plt.subplot(212) plt.title('Fast Fourier Transform') plt.ylabel('Power [a.u.]') plt.xlabel('Frequency Hz') fft1 = (Bx[51:-14]) fft2 = (By[1:-14]) for dataset in [fft1]: dataset = np.a...
Hiddenguy

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### Efficient way to calculate matrix cell distance from arbitrary coordinate in numpy

I am looking for an efficient numpy solution to the following problem: I have a N by N numpy matrix. Given an arbitrary i,j coordinate (can be decimal) of the matrix and an arbitrary range, I need to calculate the value of each cell of the matrix divided by its euclidian distance to the coordinate w...
Jakobovski

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106

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### Why does np.argwhere's result shape not match it's input?

Suppose I pass a 1D array: >>> np.arange(0,20) array([ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19]) >>> np.arange(0,20).shape (20,) into argwhere: >>> np.argwhere(np.arange(0,20)>> np.argwhere(np.arange(0,20)
user48956

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### how to handle with continuous values in array

I would like to create a submission file to the problem, but my predictions got continuous values in the array, please help me how to solve. I have array values like this: predictions array([[5.5161709e-01, 4.4297403e-01, 5.3959554e-03, 1.2935511e-05], [5.5161709e-01, 4.4297403e-01, 5.3959554e-03, 1...
suri

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### converty numpy array of arrays to 2d array

I have a pandas series features that has the following values (features.values) array([array([0, 0, 0, ..., 0, 0, 0]), array([0, 0, 0, ..., 0, 0, 0]), array([0, 0, 0, ..., 0, 0, 0]), ..., array([0, 0, 0, ..., 0, 0, 0]), array([0, 0, 0, ..., 0, 0, 0]), array([0, 0, 0, ..., 0, 0, 0])], dtype=object) N...
Nate Stemen

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182

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### Adding an array to a numpy array

I'd like to have a numpy array that looks something like this: X = np.array([[10, 20], [20, 25], [30, 16], [40, 18], [50, 90], [60, 87]]) I currently have dictionary values that I retrieve from firestore: doc_ref = db.collection('CPU Logs') query_ref = doc_ref.where(u'testData', u'==', True).order_b...
cosmo

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154

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### What is difference between parenthesis and bracket in Numpy?

Could somebody explain the difference between () and [] operations in Numpy? For example, I have run the following codes: import numpy as np x1 = np.array(([2, 9], [1, 5], [3, 6]), dtype=float) print(x1) print(type(x1)) x2 = np.array([[2, 9], [1, 5], [3, 6]], dtype=float) print(x2) print(type(x2)) y...
user10523691

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### Slicing a pattern in a large 1-d NumPy array

I have got a 1-d array where I have a pattern in the enteries. I will give an example. In the array arr, I have first 4 enteries with single digits, next 4 enteries with two digits and then the next 6 enteries with 3 digits. (This single, double, triple digit thing is just to highlight the pattern...
Sheldore

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### Pandas: How to find number of unique elements for one column coming from another column?

I have a dataframe like this: import numpy as np import pandas as pd df = pd.DataFrame({'carrier': ['c1','c1','c1','c2','c2','c2','c3','c4','c5','c5'], 'airport': ['a1','a3','a1','a1','a2','a2','a3','a4','a4','a1'], }) df carrier airport 0 c1 a1 1 c1 a3 2 c1 a1...
astro123

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5

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### LOGNORM.INV function of excel in python scipy

I need to implement the below excel function in python and need to create 10k such calculations. How can I implement this logic in scipy ? Can I use lognormal api of scipy to get lognormal inverse ? B10 - Probability event will happen C10 - Lower bound D10 - Upper bound =IF(RAND()
Bill Goldberg

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41

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### How to feed OpenCV image to a trained CNN model(add a new dimension) in Python?

I'm getting this error Error when checking input: expected conv2d_11_input to have 4 dimensions, but got array with shape (300, 300, 3) How can I pass the RGB image to a CNN? How to enumerate samples to create a 4D image?

3

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### Subtracting minimum of row from the row

I know that a - a.min(axis=0) will subtract the minimum of each column from every element in the column. I want to subtract the minimum in each row from every element in the row. I know that a.min(axis=1) specifies the minimum within a row, but how do I tell the subtraction to go by rows instead...
LeecCL137

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40

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### Pandas, groupby and counting data in others columns

I have data with four columns, that includes: Id, CreationDate, Score and ViewCount. The CreationDate has a next format, for example: 2011-11-30 19:41:14.960. I need to groupby the years of CreationDate, count them, summing Score and ViewCount also, and to add to additional columns. I want to use wi...
morris

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117

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### Fastest way to store a numpy array in redis

I'm using redis on an AI project. The idea is to have multiple environment simulators running policies on a lot of cpu cores. The simulators write experience (a list of state/action/reward tuples) to a redis server (replay buffer). Then a training process reads the experience as a dataset to gener...
Duane

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288

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### Numpy: Combine list of arrays by another array (np.choose alternative)

I have a list of numpy arrays, each of the same shape. Let's say: a = [np.array([[1, 2, 3], [4, 5, 6], [7, 8, 9]]), np.array([[11, 12, 13], [14, 15, 16], [17, 18, 19]]), np.array([[99, 98, 97], [96, 95, 94], [93, 92, 91]])] And I have another array of the same shape that gives the list indices I wan...
Max16hr

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77

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### Resample pandas dataframe and interpolate missing values for timeseries data

I need to resample timeseries data and interpolate missing values in 15 min intervals over the course of an hour. Each ID should have four rows of data per hour. In: ID Time Value 1 1/1/2019 12:17 3 1 1/1/2019 12:44 2 2 1/1/2019 12:02 5 2 1/1/2019 12:28 7 Out:...
primo7

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41

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### Max value of a Series in a single Dataframe cell

I have a Dataframe where each row contains a Series in a single column. col1 row1 [34,55,11,8] row2 [36,76,69,6] row3 [77,31,40,55] row4 [51,41,26,30] I want to get the max of each value in the series and produce that in a new column. col1 max row1 [34,55,1...
Muzz

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### Using np.where to find index of element in 2D array gives ValueError

I'm trying to use np.where to find the index of an element in an array, specifically row number I have an array of say size 1000 x 6, named 'table'. The first element in each row is a 2 x 2 string array, and the rest are 0s. Eg. a 5 x 6 example of elements in 'table': [['s',' '] 0 0 0 0 0 [' ',' '...
hskjskj

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### Increasing the speed of finding an index of an item in list

I'm trying to speed up a program I've written, and after importing cProfile, I see that one function takes up a massive bit of computation time. It's this, which finds an numpy.ndarray in a list: def locate(arr, l ): for i in range(len(l)): if np.all(l[i] == arr): return i return -1 As the list can'...
cucumber

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38

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### Number of 2D array to 3D array, extending third dimension

I have 10 different matrix of size (60, 100). I want to put them along the third dimension inside a for loop, so that the final shape is (10, 60, 100). I tried with concatenate and end up with size (600, 100).
sneha saha

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26

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### Update QpushButton icon from an numpy array don't work

I'm trying to make an icon from a numpy array displayed with matplotlib imshow. I succeed in getting colors from matplotlib into a numpy array of dimension (n*n*4) I then convert this numpy array to an Qimage then into a Qpixmap in order to update the Icon of a Qpushbutton. However the icon of the b...
ymmx

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### How to find the index of the not-null item which not in a list?

My system is python3.6, with numpy 1.16.2,scipy 1.2.1,matplotlib 3.0.3 import pandas as pd import numpy df=pd.DataFrame({'col1':['a','b','c'],'col2':['d',numpy.NaN,'c'],'col3':['c','b','b']}) df = df.astype({'col2': 'category'}) print(df) output of above script is: col1 col2 col3 0 a d...
kittygirl

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### What's the difference between shape(150,) and shape (150,1)?

What's the difference between shape(150,) and shape (150,1)? I think they are the same, I mean they both represent a column vector.
Lisa

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44

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### Summing selected elements of a matrix in Python

I have a [n x n] matrix containing values belonging to different groups, and a [1 x n] vector defining to which group each element belongs. (n usually ~1E4, in this example n=4) I want to calculate a matrix obtained by summing together all the elements belonging to the same group. I use np.where() t...
user9998992

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130

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### Performing calculations on a numpy array and adding them to a pandas dataframe

Let's say I have an array such as this: a = np.array([[1, 2, 3, 4, 5, 6, 7], [20, 25, 30, 35, 40, 45, 50], [2, 4, 6, 8, 10, 12, 14]]) and a dataframe such as this: num letter 0 1 a 1 2 b 2 3 c What I would then like to do is to calculate the difference between the first and last...
top bantz

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25

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### Blockwise reshape in numpy?

I have a numpy array with columns that are in blocks. I want to transpose the blocks. It's conceptually simple, and I guess one can do it simply, but I dont know how. Given a numpy array on block form np.hstack(list_of_blocks), I want to get np.vstack(list_of_blocks). To make it more precis, I want...
LudvigH

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38

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### Faster way to modify a numpy array

I have a large numpy array with 4 million rows and 4 columns (shape = (4000000,4)) I need to modify/ decrease the number of rows, based on the value in fourth column. For example few of my rows in my data set look like the following: a = np.array([[1.32, 24.42, 224.21312, 0],[1.32, 24.42, 224.21312...
Jesh Kundem

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22

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### How to delete images with the low pixel value in a folder

I have some problems with removing images in a folder The followings are what I have done. import os,glob from PIL import Image from skimage import io import numpy as np path = '/Users/Xin/Desktop/SVM-Image-Classification-master/Folder' # Delete images with the low pixel value for filename in os.lis...
Xin Zhang

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### “Rank” DataFrame columns per row

Given a Time Series DataFrame is it possible to create a new DataFrame with the same dimensions but the values are the ranking for each row compared to other columns (ordered smallest value first)? Example: ABC DEFG HIJK XYZ date 2018-01-...
Ewan

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47

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### How to select the smallest number within one row in python?

I have data with multiple numbers in each row like this: gene numbers P53 11 11 11 7 13 8 8 ACE 6 5 4 5 3 BRCA 2 2 1 I want the numbers column to only contain the smallest number that is in that row, with output being for example: gene numbers P53 8 ACE 3 BRCA 1 I have lo...
DN1

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### Numpy: Pick elements based on bool array

I've got an array and a boolean array (as one hot encoding) a = np.arange(12).reshape(4,3) b = np.array([ [1,0,0], [0,1,0], [0,0,1], [0,0,1], ], dtype=bool) print(a) print(b) # [[ 0 1 2] # [ 3 4 5] # [ 6 7 8] # [ 9 10 11]] # [[ True False False] # [False True False] # [False False True]...

1

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### Value Error Converting the datatype of elements in an array

Im trying to put all matching elements in two different arrays into a singular one. However I'm running into a type error that I'm not entirely sure about. This is what I initially tried to do: IRS_zips = AGI.zipcode.unique() # np array of type int medi_zips = df.nppes_provider_zip.unique() # np ar...
Sebastian Goslin

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### How to sum up for each distinct value c in array X all elements Y[i] where X[i] = k efficiently?

Given an 1D array X of length n in Numpy with k distinct values, I want to sum up for each of these distinct values c in another 1D array Y with the same length, all those elements Y[idx] where X[idx] == c in the most efficient way. Example: X = [1, 3, 2, 1, 2] and Y = [0.1, 0.2, 0.5, 2.0, 0.3]. The...
fwilhelm

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### How does Python convert date value from excel

I am reading a csv file with a CDATE column. The structure of the column is: |CDATE | |08/28/2018| |08/28/2018| |08/29/2018| |08/30/2018| |09/02/2018| |09/04/2018| ... |04/10/2019| As you can see there is duplicate date as well as missing dates in this column, and I would like to find the missin...
user1759827

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### Python ValueError. Don't understand error or how to fix

I am following the tutorial here; https://www.analyticsvidhya.com/blog/2018/10/predicting-stock-price-machine-learningnd-deep-learning-techniques-python/#comment-155692 Instead of using the provided dataset I am using one needed for my assignment. The code used is #import packages import pandas as p...
Dzl

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### columns as a paramater in .at[] in python

I want to fill a dataframe's row proper values for proper columns I am trying to reach a column by a parameter but I can not. If I send the name as string it works fine. The dataframe has the column that I am trying the reach. list = key_queue.get() column_name = column_name_queue.get() print(column...
James

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### How to remove duplicates and force elements in a numpy array to be unique using a given range?

In case of differential evolution, during mutation, the formula that is used most often is arr[a] = (arr[b] + M * (arr[c] - arr[d])) % arr.shape[1] Where arr is a 2d array consisting of non-negative integers such that all elements in each row are unique, a represents each row of arr, M is the mutat...
Somnath Rakshit

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3

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### How to add magnitude or value to a vector in Python?

I am using this function to calculate distance between 2 vectors a,b, of size 300, word2vec, I get the distance between 'hot' and 'cold' to be equal 1. How to add this value (1) to a vector, becz i thought simply new_vec=model['hot']+1, but when I do the calc dist(new_vec,model['hot'])=17? import...

1

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### Iterating through data frame to buy or reject stocks

I have created the following dummy data for (1 year of stock prices) df = pd.DataFrame(np.random.uniform(100,200, size = (365,1)), index=list_dates, columns=list('A')) df.head() Following is the head from the data frame. A 2018-01-01 151.034052 2018-01-02 157.682393 2018-01-03 134.194843 2018-01-...
Hackerds

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12

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### Numpy outer equality comparison with more than one element

I have two numpy arrays with which I'm doing an outer equality comparison m = np.random.randint(4,size=(4,4,4)) ar = np.array([1,2,3]) x = np.equal.outer(ar,m) This works well if I'm interested in testing every single element of ar in m. But what if I'd like to do more than one comparison in one go,...
HappyPy