CODEWITHSUNDEEP
pythonnumpymean
Julep
Julep

Reputation: 790

Compute mean of last X elements of a list in Python2.7

Is there an elegant way or function to compute the mean of the last X elements of a list?

I have a list register that increases in size at each iterations :

register = np.append(register, value)

I want to create another list in which an i element corresponds to the mean of the X last elements in register

register_mean[i] = np.mean(register[i-X:i])

The tricky part is for the first X iterations, when there isn't X values yet in register. For these specific cases, I would like it to compute the mean on the firsts values of register, and only take the first value of register as first value of register_mean.

This could be done during the iterations or after, when register is complete.

I know there is lots of similar questions but haven't found one that answered this particular problem

Upvotes: 0

Views: 2128

Answers (2)

Andrea S.
Andrea S.

Reputation: 410

If I understand your question correctly, this should do the work:

X = 4 # Span of mean
register_mean = [np.mean(register[max(i-X, 0): max(i-X, 0) + 1]) for i in range(len(register))]

It will essentially create a moving average of the register elements between i - X and i; however, whenever i - X is negative, it will only take the values between 0 and i + 1.

Upvotes: 0

Count Zero
Count Zero

Reputation: 146

Could it be something as simple as 

if X < i:
 register_mean[i] = np.mean(register[:i])

This just averages however many prior points there are until you have enough to average X points

Perhaps I misinterpreted your intent!

Upvotes: 2

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