Averaging column 2D array python

Question

I have a 2D arraylist data which fills with a loop like this:

data.append([TrueID,rssi])

after 8 times i got this value for data:

data =

    [['469420270013002A', -90], 
     ['469420270005000C', -89], 
     ['469420270013002A', -94], 
     ['4694202700270003', -53], 
     ['469420270005000C', -91], 
     ['469420270013002A', -92], 
     ['4694202700270003', -55]]

I want to calculate the average RSSI value of each TrueID and return the lowest RSSI value with its TrueID.

So I need output:

print "The weakest ID is " ID_result " with Rssi value of " rssi_result
>>The weakest ID is '4694202700270003' with Rssi value of -54

It's necessary the 2D array fills until 20 values and continues like a FIFO system.

All suggestions are welcome (even if you know other methods to get to the same result)!

Thank you!

-54 is actually going to be the maximum value here.

Ashwini Chaudhary
– Ashwini Chaudhary

2013-12-01 21:52:46 +00:00
Commented Dec 1, 2013 at 21:52 — Ashwini Chaudhary
– Ashwini Chaudhary, Commented Dec 1, 2013 at 21:52
Please provide example code of what you have tried.

Michael Peterson
– Michael Peterson

2013-12-01 22:05:06 +00:00
Commented Dec 1, 2013 at 22:05 — Michael Peterson
– Michael Peterson, Commented Dec 1, 2013 at 22:05

Ashwini Chaudhary · Accepted Answer · 2013-12-01 21:52:15Z

1

Use collections.defaultdict and max:

>>> from collections import defaultdict                                   
>>> lis = [['469420270013002A', -90],                                 
     ['469420270005000C', -89], 
     ['469420270013002A', -94], 
     ['4694202700270003', -53], 
     ['469420270005000C', -91], 
     ['469420270013002A', -92], 
     ['4694202700270003', -55]]
>>> d = defaultdict(list)                
>>> for k, v in lis:                                                      
    d[k].append(v)
...

Now d contains:

>>> d
defaultdict(<type 'list'>,
{'469420270005000C': [-89, -91],
 '4694202700270003': [-53, -55],
 '469420270013002A': [-90, -94, -92]})

Now use max and a dict comprehension to calculate the average and find out the max (key, value) pair:

>>> max({k:sum(v)/float(len(v)) for k, v in d.items()}.items(), key=lambda x:x[1])
('4694202700270003', -54.0)

answered Dec 1, 2013 at 21:52

Ashwini Chaudhary

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3 Comments

user3055369 Over a year ago

Thank you Ashwini Chaudhary! It works like u said, 1 more thing: How to do after 20 values overwrite the original values like a fifo system ?

Ashwini Chaudhary Over a year ago

@user3055369 Use collections.deque with maxlen=20, to get a FIFO system.

user3055369 Over a year ago

I solved this by using append and pop: lis.append([TrueID,rssi]) d2counter += 1 if d2counter >= 20: lis.pop(0)

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