numpy indexing

Official documents

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Tips

Numpy配列のAdvanced Indexingは知らないとわけわからなくなる。([], compare, condition, 条件式, fancy indexing ) - Qiita

MetPy Mondays '#90 - What is a NumPy Axis? : Unidata Developer's Blog

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Examples

When f contains frequencies and P contains spectral density, the top 10 corresponding frequencies in descending order of 𝑃

code:python

code:python

import numpy as np

# lon: longitude lat:latittude

xrange=np.logical_and(lon>=120.,lon<=180.)

yrange=np.logical_and(lat>=20.,lat<=45.)

range selection 2

code:python

import numpy as np

# lon: longitude lat:latittude

xrange=((lon>136.) & (lon<140.))

yrange=((lat>36) & (lat<38))

range selection 3

code:python

import numpy as np

# lon: longitude lat:latittude

find nearest value in numpy array

code:python

import numpy as np

def find_nearest(array,value):

idx=(np.abs(array-value)).argmin()

find index where 2-dimensioal (multi-dimensional) array has maximum or minimum

code:python

ans=np.where(a == a.max())

i,j = np.unravel_index(a.argmax(), a.shape)

The index at which the array 'walk' first exceeds 10.

code:python

code:python

a=np.arange(5)

Tips

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code:python

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Useful methods

argmax()

argmin()

searchsorted()

argsort()

argwhere()