CODEWITHSUNDEEP
pythonalgorithmperformancepython-2.7numpy
Reactionic
Reactionic

Reputation: 194

Fastest way to find maximum value of a list in specific intervals

I have a list that contains 1024 elements. I want to check the maximum value of the list between an interval that i determined.

for example X is my list that is in numpy array form. Then;

if np.amax(X[0:31]) > 200:
    print("1")
elif np.amax(X[0:31]) < 200:
    print("1a")

if np.amax(X[32:63] > 200:
    print("2")
elif np.amax(X[32:63] < 200:
    print("2a")

and if - elif statements goes untill X[992:1023]. That means there are 16 intervals and 16 if-elif statements. Is there more efficient way to do that?

edit:Thanks for the answer. But the problem is a bit different. Let me try to explain it with an example. Each result of these intervals lights up an LED. There are 16 intervals and 16 different LEDs. Further more maximum value bounds have 3 layer. I did not mention about it. But such as (max<200), (200>max<500), (max > 500). It is a bit complicated.

Upvotes: 0

Views: 2131

Answers (2)

jusx
jusx

Reputation: 1327

You could reshape your matrix to a two dimensional matrix based on your interval and use the max function on a specific axis.

interval = 32
Xnew = X.reshape(interval, len(X)/interval)
print np.max(Xnew, axis=1)  # This is an array of the max values of each consecutive interval range in X

Upvotes: 0

user2390182
user2390182

Reputation: 73460

Well, for such regular intervals, a standard for-loop should do. For starters, this will work:

for x in xrange(0, 1024, 32):  # 0, 32, 64, ... , 992
    m = np.amax(X[x:x+32])
    if m > 200:
        print(str(x/32 + 1))  # 1, 2, 3, ... , 32 (not 16)
    elif m < 200:
        print(str(x/32 + 1) + 'a')  # 1a, 2a, 3a, ...

I assumed that you want to include index 31 in the first interval. Your code will omit indexes 31, 63, etc.

Upvotes: 1

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