How to scale down a list of integers-CodePudding

I have a list, that can be of various lengths (less than 100 or more than 1.800.000) and I need to display all those values on a graph (a waveform) of 800 points on which I can draw.

I have tried taking a value for every step, where a step is the list length / 800. And it is the closest I can get to. I have tried taking the average value of the n surrounding of step with various n, but I can't get a waveform that satisfies me.

I know image compression work by taking an average of surrounding pixels, and I am trying to do the same with a list of values going from 0 to 200. I need to preserve the global aspect, but also the highest and lowest spikes.

CodePudding user response：

First of all this is more resampling than scaling. As mentioned in the comments you have 2 cases:

upscaling/sampling n<800

this is relatively simple you just interpolate the missing values. I would go for Python code :

numberOfSmallerList = 400
small_list_len = int(len(big_list) / numberOfSmallerList)

finalPointsToPlot = []

for i in range(0, len(big_list), small_list_len):
    biggestDiff = max(big_list[i:i small_list_len]) - 
    min(big_list[i:i small_list_len])

    finalPointsToPlot.append(biggestDiff/2   100)
    finalPointsToPlot.append(100 - biggestDiff/2)


import matplotlib.pyplot as plt
plt.plot(finalPointsToPlot)
plt.show()