How do I get my python function to use an array as input?

Question

I have this python function that calculates day length depending on latitude and day of the year (source : https://gist.github.com/anttilipp/ed3ab35258c7636d87de6499475301ce).

def daylength(dayOfYear, lat):
    latInRad = np.deg2rad(lat)
    declinationOfEarth = 23.45*np.sin(np.deg2rad(360.0*(283.0+dayOfYear)/365.0))
    if -np.tan(latInRad) * np.tan(np.deg2rad(declinationOfEarth)) <= -1.0:
        return 24.0
    elif -np.tan(latInRad) * np.tan(np.deg2rad(declinationOfEarth)) >= 1.0:
        return 0.0
    else:
        hourAngle = np.rad2deg(np.arccos(-np.tan(latInRad) * np.tan(np.deg2rad(declinationOfEarth))))
        return 2.0*hourAngle/15.0

where dayOfYear : int and lat : float

How do I adapt this so lat uses the values from my array latarray to create a new array of the same .shape(883,1368) ?

Carsten · Accepted Answer · 2019-06-06 15:20:44Z

1

How about a list comprehension? Then you don't need to change your function:

[daylength(dayOfYear, lat) for lat in latarray]

answered Jun 6, 2019 at 15:20

Carsten

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1 Comment

David Zemens Over a year ago

or map: list(map(lambda x: daylength(dayOfYear, x), latarray))

jose_bacoy · Accepted Answer · 2019-06-06 15:46:38Z

0

You can use vectorize function in your array and it will apply your function in each element in the array latarray. See demo below:

import numpy as np
vfunc = np.vectorize(daylength)
dayOfYear = 100
latarray = np.array([[10, 20, 30], [3, 6, 9]])
vfunc(dayOfYear, latarray)

Result:
array([[12.16899985, 12.34893859, 12.5537987 ],
       [12.05022628, 12.10073141, 12.1518005 ]])

Reference: https://docs.scipy.org/doc/numpy/reference/generated/numpy.vectorize.html

answered Jun 6, 2019 at 15:46

jose_bacoy

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Comments

wjandrea · Accepted Answer · 2019-06-06 15:40:19Z

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value=np.zeros((883,1368))

for i in range(np.size(latarray,0)):
    for j in range(np.size(latarray,1)):
         value[i,j] = daylength(DayOfYear, latarray[i,j])

edited Jun 6, 2019 at 15:40

wjandrea

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answered Jun 6, 2019 at 15:24

pedro_galher

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