Problemas com index out of range

[leandro Riato]

Estou tendo problemas com o índex de um loop for
Algoritmo:

similarity = []
sample1 = []
sample2 = []
least_frequent_ = []
engine_phase_high_filtered = [20, 20, 20, 20, 2, 2, 2, 2, 20, 20, 20, 20, 20, 20, 20, 2, 2, 2, 2, 20, 20, 20, 20, 20, 20, 20, 2, 2, 2, 2, 20, 20, 20, 20, 20, 20, 20, 2, 2, 2, 2, 20, 20, 20, 20, 20, 20, 20, 2, 2, 2, 2, 20, 20, 20, 20, 20, 20, 20, 2, 2, 2, 20, 20, 20, 20, 2, 2, 2, 2, 20, 20, 20, 20, 20, 20, 20, 2, 2, 2, 2, 20, 20, 20, 20, 20, 20, 20, 2, 2, 2, 2, 20, 20, 20, 20, 20, 20, 20, 2, 2, 2, 2, 20, 20, 20, 20, 20, 20, 20, 2, 2, 2, 2, 20, 20, 20, 20, 20, 20, 20, 2, 2, 2, 20, 20, 20, 20, 2, 2, 2, 2, 20, 20, 20, 20, 20, 20, 20, 2, 2, 2, 2, 20, 20, 20, 20, 20, 20, 20, 2, 2, 2, 2, 20, 20, 20, 20, 20, 20, 20, 2, 2, 2, 2, 20, 20, 20, 20, 20, 20, 20, 2, 2, 2, 2, 20, 20, 20, 20, 20, 20, 20, 2, 2, 2]

def find_least_frequent(filtered_signal):
    least_frequent_.clear()
    frequent = mode(filtered_signal)
    for i in range(0, len(filtered_signal)):
        if filtered_signal[i] != frequent:
            least_frequent_.append(i)
    i = None
    del i
    return least_frequent_

def search_by_similarity(leastfreq, filteredsignal):
    sample1.clear()
    sample2.clear()
    fullcycle = []
    fullcycle.clear()
    similarity.clear()
    for i in range(0, round(len(leastfreq)/2)):
        for j in range(0, leastfreq[i+1]-1):
            sample1.append(filteredsignal[j])
        j = None
        for j in range(leastfreq[i+1], leastfreq[i+1] + len(sample1)):
            sample2.append(filteredsignal[j])
        j = None
        if len(sample1) == len(sample2):
            for j in range(0, len(sample1)):
                if sample1[j] == sample2[j]:
                    similarity.append(True)
            j = None
            if ((len(similarity)/len(sample1)*100)) >= 95:
                fullcycle = sample1
    i = None
    return(fullcycle)

least_frequent = find_least_frequent(engine_phase_high_filtered)
search = search_by_similarity(least_frequent, engine_phase_high_filtered)

 

Preciso que esse algoritmo encontra um ciclo que tenha 95% ou mais de precisão nos valores.