python for loop to calculate mean value for each array segment

Question

I got a formal problem by using python and some for loops for each segment of my lists to be averaged.

I have an array of x=(epochs, 257)
Now I want to calculate for every epoch the mean value of the 257 values in there
The output should be an array of x _ mean = (120, 1)

I used a for loop, but the results are more than questionable. Any help is appreciated.

x_mean=np.zeros (epochs, 1) For i in range (0, epochs): x_mean [i] = np.mean (x [i]) <---- that's my approach. ..I like to work with numpy more than using uncomfortable other stuff... — Daniel Velden
– Daniel Velden, Commented May 30, 2015 at 6:34

dlask · Accepted Answer · 2015-05-30 07:49:45Z

1

a = [[1, 2, 3, 4], [2, 3, 4, 5], [3, 4, 5, 6]]
b = [float(sum(x))/len(x) for x in a]

Simply, you select all sublists and you calculate the average of each sublist in a standard way, e.g. sum/len.

The only potentially dangerous part is the divide operation. If the list contains only integers also the sum is integer. The len is integer automatically. Python 2 (in contrary to Python 3) uses integer-division when both numerator and denominator are integers so 2/3 -> 0. To prevent this we can convert e.g. the numerator to float.

edited May 30, 2015 at 7:49

answered May 30, 2015 at 5:32

dlask

9,0421 gold badge29 silver badges31 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Daniel Velden Over a year ago

Nope way to uncomfortable.... look up ...numpy and just use numpy.mean (x) .....But I do like your approach. ..Thank you I think it is helpful....sometimes you Programm and miss the tree for the wood

Daniel Velden Over a year ago

after modifying your sugestion it fits in my code somehow...thank you for your help

Daniel Velden · Accepted Answer · 2015-07-21 07:10:52Z

0

np.mean(x, axis=0)

is the solution, thanks for trying so hard. and thanks for posting comments just because.

answered Jul 21, 2015 at 7:10

Daniel Velden

1792 silver badges17 bronze badges

1 Comment

dlask Over a year ago

Please use the numpy tag in your question next time in order to emphasize that you are interested in the numpy-based solution.

Collectives™ on Stack Overflow

python for loop to calculate mean value for each array segment

2 Answers 2

2 Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related