Averaging AtoD samples

**mackrackit** · - 29th August 2010, 19:26

The first 10 would be tossed but the second 10 would not because now the pairs are 10,10,11...

**HankMcSpank** · - 29th August 2010, 19:57

Originally Posted by mackrackit

The first 10 would be tossed but the second 10 would not because now the pairs are 10,10,11...

Aah...ok, gotcha.

Actually my example 'data series' wasn't a good one, as the data values would actually be in the hundreds (vs units which I used), which allows percentages to be used.

So, assuming a series of data coming into a variable called 'sample'...

Code:

' compare a pair called value & value2 from the incoming 'sample'

value = sample     '

upper_window = value2+(value2*4/100) 'create a window 4% above previous sample
lower_window = value2-(value2*4/100)  'create a value 4% below previous sample

if (value>= lower_window) AND (value <= upper_window) then incoming 'sample is within 'allowable error window'?
gosub average 'goto averaging routine
endif
value2 = value1

etc

would something like the above work?#

Edit: Just seen your post/link scalerobotics - off to have reader's digestion! (& yes, I did a search but I guess my keywords weren't erhm key)

**HankMcSpank** · - 23rd September 2010, 22:18

ok, so scalerobotic's link to Melanie's 'sorting numbers' article, is exactly what I need, so I'm trying to get the thing to work.

i've basically got a small array that a prepopulate with some random numbers.

Code:

@ __CONFIG _FCMEN_OFF & _HS_OSC & _WDT_OFF & _MCLRE_OFF & _CP_OFF & _IESO_OFF & _BOR_OFF & _PWRTE_OFF

DEFINE  OSC 20          ' set Oscillator at 20Mhz.
DEFINE  NO_CLRWDT 1   ' PBP doesn't clear WDT automatically
DEFINE HSER_CLROERR 1
DEFINE HSER_TXSTA 24h ' Enable transmit
DEFINE HSER_SPBRG 129 ' set USART to 9600 baud  @20Mhz

    CounterA var Byte
    DataA var Byte
    RawData var Byte [6]
    Averaged var byte
    hserout [27,91,72]          'home cursor
    hserout [27,91,50,74]       'clear screen
    
    RawData[0]  = 25
    RawData[1]  = 27
    RawData[2]  = 32
    RawData[3]  = 30
    RawData[4]  = 34
    RawData[5]  = 33

    
    hserout ["before....", 13, 10]
    hserout [dec rawdata[0],13,10]
    hserout [dec rawdata[1],13,10]
    hserout [dec rawdata[2],13,10]
    hserout [dec rawdata[3],13,10]
    hserout [dec rawdata[4],13,10]
    hserout [dec rawdata[5],13,10]
    hserout [13,10]
    hserout [13,10]


    CounterA =0
    gosub SortArray
    gosub Average_data
    hserout ["after....", 13, 10]
    hserout [dec rawdata[0],13,10]
    hserout [dec rawdata[1],13,10]
    hserout [dec rawdata[2],13,10]
    hserout [dec rawdata[3],13,10]
    hserout [dec rawdata[4],13,10]
    hserout [dec rawdata[5],13,10]

    hserout ["averaged = ", dec averaged,13,10]
    goto end1
    
    
Average_data:
    hserout [dec rawData[2]," + ", dec rawData[3], 13,10]
    Averaged = (rawData[2]+rawData[3])/2    ' average the middle two of 6 ongoing samples
    return

SortArray:
SortLoop:
    If RawData(CounterA+1) < RawData(CounterA) then
        DataA=RawData(CounterA)
        RawData(CounterA)=RawData(CounterA+1)
        RawData(CounterA+1+0)=DataA
        If CounterA > 0 then CounterA=CounterA-2
        endif
    CounterA=CounterA+1
    If CounterA < 5 then goto SortLoop
    Return

    end1:
    end

here's my screen output (I average the middle two numbers Rawdata[2] & RawData[3] )....

Code:

before....
25
27
32
30
34
33

after....
6
25
27
30
32
33
averaged = 31

It all works (ie sorts & averages correctly) - but where on earth has the number 6 in the sorted numbers come from? (there was no number six in the original array - also, whatever number I place in that array position RawData[4] comes out sorted as 6!?!!)

Edit: Ok, think I've stumbled on the issue - it seems to be related to my array declaration ....because when I use RawData var Byte [8] ...everything works.

So why can't I declare an array 5 bytes 'deep'? ie RawData var byte [5] ???

**aratti** · - 24th September 2010, 07:30

It all works (ie sorts & averages correctly) - but where on earth has the number 6 in the sorted numbers come from?

Check out the sorting routine because it doesn't work. The first number should be 25, while the last number should be 34 not 33.

Also your average is not correct, since 27 + 30 / 2 = 28.5 (28 as integer) not 31

Very likely the error comes from the wrong sorting.

Cheers

Al.

**Ioannis** · - 24th September 2010, 07:47

I suppose that you corrected the array definition from[6] to [5].

And then the check in the program:

Code:

If CounterA < 5 then goto SortLoop

to this:

Code:

If CounterA < 4 then goto SortLoop

Ioannis

**HankMcSpank** · - 24th September 2010, 10:33

Guy - what can I say

.....I initially used random 1-6 for my numbers in the array & it sorted them & averaged them fine! (ie 1,2,3,4,5,6 was the screen output!)

I'm puzzled why my screen output posted above doesn't look like it's working (for either the sorting or the averaging!! lol) - it was late ...that's my lame excuse for not picking up on that! The 'sorting' part of the code was a direct lift from Melanie's article.

I'm at work now (don't tell my boss!) , so will revisit this tonight.

**HankMcSpank** · - 25th September 2010, 10:37

Ok, the thread title really ought to be called stripping out erroneous samples & then averaging the leftovers (vs averaging data which includes erroneous samples), I've revisited my earlier problem

Code:

@ __CONFIG _FCMEN_OFF & _HS_OSC & _WDT_OFF & _MCLRE_OFF & _CP_OFF & _IESO_OFF & _BOR_OFF & _PWRTE_OFF

DEFINE  OSC 20          ' set Oscillator at 20Mhz.
DEFINE  NO_CLRWDT 1   ' PBP doesn't clear WDT automatically
DEFINE HSER_CLROERR 1
DEFINE HSER_TXSTA 24h ' Enable transmit
DEFINE HSER_SPBRG 129 ' set USART to 9600 baud  @20Mhz

ANSEL       =  0
ANSELH     =  0

    CounterA            var Byte    'A counter for sorting out the erroneous data
    DataA               var word    'A Variable used in sorting the numbers in the array 
    RawData             var word [6] 'This is the RawData gojng into the array
    Averaged            var word     'This is used to get the average.
  
    top:    
    RawData[0]  = 300
    RawData[1]  = 100
    RawData[2]  = 200
    RawData[3]  = 600
    RawData[4]  = 400
    RawData[5]  = 500

    pause 250
  
    hserout [27,91,72]          'home cursor
    hserout [27,91,50,74]      'clear screen  
    
   next1:
    hserout [13,10]
    hserout [13,10]
    pause 300 
    hserout ["before....", 13, 10]
    hserout [13,10]
    hserout [dec rawdata[0],13,10]
    hserout [dec rawdata[1],13,10]
    hserout [dec rawdata[2],13,10]
    hserout [dec rawdata[3],13,10]
    hserout [dec rawdata[4],13,10]
    hserout [dec rawdata[5],13,10]
    hserout [13,10]
    hserout [13,10]

    pause 2000
    
    CounterA =0
    gosub SortArray
    gosub Average_data
    hserout ["after....", 13, 10]
    hserout [13,10]
    hserout [dec rawdata[0],13,10]
    hserout [dec rawdata[1],13,10]
    hserout [dec rawdata[2],13,10]
    hserout [dec rawdata[3],13,10]
    hserout [dec rawdata[4],13,10]
    hserout [dec rawdata[5],13,10]
    hserout [13,10]
    hserout ["therefore, middle two samples are ", dec rawData[2]," + ", dec rawData[3], 13,10]
    pause 500
    hserout [13,10]
    hserout ["averaged middle two samples = ", dec averaged,13,10]
    pause 500
    pause 3000
    goto top
    
    
Average_data:
    Averaged = (rawData[2]+rawData[3])/2    ' average the middle two of 6 samples
    return

SortArray:
SortLoop:
    If RawData(CounterA+1) < RawData(CounterA) then
        DataA=RawData(CounterA)
        RawData(CounterA)=RawData(CounterA+1)
        RawData(CounterA+1+0)=DataA
        If CounterA > 0 then CounterA=CounterA-2
        endif
    CounterA=CounterA+1
    If CounterA < 5 then goto SortLoop
    Return

    end

And it works (basically, the code throws away all but the middle two samples of six & averages those two - ideal if your input data is all over the place.,...eg comparator counts etc!)...

Code:

before....

300
100
200
600
400
500


after....

100
200
300
400
500
600

therefore, middle two samples are 300 + 400

averaged middle two samples = 350

Or a more real world example (eg a comparator interrupt count jittering in or around the 200 count level but with one spurious/erroneous count of 400 in the 'sample of six' to get rid of)...

Code:

before....

199
400
200
200
199
200


after....

199
199
200
200
200
400

therefore, middle two samples are 200 + 200

averaged middle two samples = 200

Not entirely sure what the problem was (I changed a few things at once & didn't retrace my steps!)

**aratti** · - 25th September 2010, 10:42

That's better!

Cheers

Al.

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