Generating sequence of numbers in Python (curved)

Question

I am trying to generate, say a non-linear sequence of 120 numbers in a range between 7 and 20.

I have already tried using numpy geomspace and logspace, which gave me pretty much the same outcome. It does what I want, but the resulted "curve" is not "sharp" enough so to speak.

import numpy as np
TILE_NONLINEAR = np.geomspace(7, 20, num=120)

I need to control an acceding and descending. A slow start and fast acceleration at the end and/or vice versa. Like for instance, outcome should be something like:

[7, 7.001, 7.003, 7.01 ..... 17.1, 17.3, 17.8, 18.7, 20]

or

[7, 7.8, 8.5, 9, ..... 19.9, 19.95, 19.98, 20]

The resulted sequences are off the top of my head just to give an idea.

Like an animation tweening curve. The rate of change is slower at the beginning and ending and faster in the middle. — Dan D.
– Dan D., Commented Jul 20, 2019 at 21:34
lol, yeah. I am writing a routine inside Python API interface of the animation app. I'd be glad to use built-in curves, but unfortunately I need to write on every frame in this case. Thus generating sequence manually. — EvolveX
– EvolveX, Commented Jul 20, 2019 at 21:39

Masoud · Accepted Answer · 2019-07-21 08:41:05Z

2

There are bunch of nonlinear function that can be used for the task (some are listed here). Below is a simple exponential function to generate nonlinear array between two numbers. You can control curvature in the function:

import numpy as np

def nonlinspace(start, stop, num):
    linear = np.linspace(0, 1, num)
    my_curvature = 1
    curve = 1 - np.exp(-my_curvature*linear)
    curve = curve/np.max(curve)   #  normalize between 0 and 1
    curve  = curve*(stop - start-1) + start
    return curve

arr = nonlinspace(7, 21, 10)

#rounded result : [ 7., 9.16, 11.1, 12.83, 14.38, 15.77, 17.01, 18.12, 19.11, 20.]

answered Jul 21, 2019 at 8:41

Masoud

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1 Comment

EvolveX Over a year ago

Perfect, Thank you!

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