# Questions tagged [numpy]

NumPy is an extension of the Python language that adds support to large multidimensional arrays and matrixes, along with a large library of high-level mathematical functions for operations with these arrays.

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### In NumPy: How to detect whether an argument is a "ragged nested sequences"

If obj is a list of "ragged nested sequences", like obj = [1, 2, [3, 4]], then np.array(obj) produces a warning: "Creating an ndarray from ragged nested sequences ... is deprecated...&...

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### how to change shape of 3d array

I have a 3d array in shape (288,512,512) that 288 is the number of images and 512*512 is the width and height of the image. Also, there is a mask array of this image in shape (512,512,288). How can I ...

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### How to set second and following occurrences of 0 to NaN in python

I am trying to figure out how to set all second occurrences of 0 in my dataframe to NaN in python. However, this is a tranposed dataframe so 0 would occur across the columns. To explain, I have the ...

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### BUILD FAIL ON HEROKU

Trying to deploy a python application on Heroku, however it fails in building with the following log: Building wheels for collected packages: numpy, pandas, scikit_learn, tornado, blinker, ...

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### Saving a CV2 numpy array to SVG file format

I am working on a document image analysis project. Part of the work is to capture an image (usually contains text in the form of tables) from the document and embed it in the html file. For now, I ...

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### How to grab corresponding values from two-dimensional numpy array

I have a two-dimension array [[ 1, 4, 4, 6, 6, 6, 8, 8, 8, 8, 9, 9, 9, 9, 9, 10, 11, 11, 11, 11, 11], [ 0, 0, 1, 0, 1, 4, 0, 1, 4, 6, 0, 1, 4, 6, 8, 5, 0, 1, 4, 6, 8]...

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### How to draw a straight line between two points on a heatmap

I am creating a 2D matplotlib plot (i and j coordinates) which contains 10 subplots. Each subplot contains 150 by 150 grid cell data. How can I insert a thick straight line arrow (color = red) that ...

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### trying to get ratio of numbers in a rolling window. TypeError: unsupported operand type(s) for /: 'Rolling' and 'int'

im trying to get the ratio of numbers of a certain column that are above 0 in a rolling window as a new column. i tried the following: df['ratio'] = pd.DataFrame.rolling(df[df['column']>0].count(),...

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### Numpy - Map data to a matrix based on index location

First, I am only assuming Numpy is the best way to do this, but I'm open to other better suited packages (pandas?). I am looking to map the following data into a matrix format (to eventually display ...

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### How to mask only the most recent date?

Let's say I have 2 days worth of date times: import pandas as pd import numpy as np index = pd.date_range("2020-01-01 00:00:00", "2020-01-03 00:00:00", freq="15T") ...

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### Python find the long axis of a 3D point cloud or 3D hull

I am trying to find the 'long axis' of a 3D object (described as a 3D boolean or label array), which passes through (or near) the centroid of that object. I would like to think I could simply iterate ...

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### pandas dtypes column coercion

What would cause pandas to set a column type to 'object' when the values I have checked are strings? I have explicitly set that column to "string" in the dtypes dictionary settings in the ...

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### Difference of Numpy Dimension Expand code

I got confuse between two Numpy dimension expand code. First code is X[:, np.newaxis]. Second code is X[:, np.newaxis, :]. I ran this code on Jupyter, But it returns same shape and result. What is the ...

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### How to combine or join unique values from different columns in DataFrame?

This is my Dataset and I want to combine Symptom_1, Symptom_2, Symptom_3. The code that I used to combine them is df['Symptom'] = df.apply(lambda row: row.Symptom_1 + row.Symptom_2 + row.Symptom_3, ...

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### Solve very large system of linear equations with Numpy

I'm trying to solve a system of equations that is a 1 Million x 1 Million square matrix and one 1 Million solution vector. To do this, I'm using np.linalg.solve(matrix, answers) but it's taking a very ...