Arduino: smoothing series of numbers

The most reliable method I found when I experienced the same problem was
just dividing the input in order to limit the range. There may be a better
solution out there, but this is probably the most simple. Might also be
worth dividing the signal at the arduino side if you want to save CPU
cycles.

On 14/03/2008, Jeff Thompson wrote:
>
>
> So I have my Arduino, running a slightly modified Arduino2Max and reading
> the analog pins from a potentiometer. I can get the numbers into Max no
> problem, but there's some jitter when the pot is still (fluctuating up and
> down about 5 values).
>
> I'd like to smooth those out to get an average. I tried using peak, which
> works great for numbers going up, but not down.
>
> The mean object works, but when ramping up or down it takes those into the
> equation.
>
> Any help would be appreciated. This seems like there must be a very
> simple solution.
>
> Thanks!
>
> Jeff
>

You could just smooth them over a short time span using [line] or
[line] depending on your needs. This will compromise the
responsiveness slightly, but you can tweak it for the optimum
tradeoff. I use something like the attached patch for a number of
uses, mostly for smoothing out discontinuities in incoming data, but
it might serve your purposes, as well. Alternatively you could use
something like [past] to create an auto-adjustable threshold for
accepting input if it exceeds the amplitude of the input jitter.
Perhaps some combination of the two might work even better?

save as control-smooth.mxb:

save as control-smooth.help

On Mar 14, 2008, at 12:49 PM, Jeff Thompson wrote:

>
> So I have my Arduino, running a slightly modified Arduino2Max and
> reading the analog pins from a potentiometer. I can get the
> numbers into Max no problem, but there's some jitter when the pot
> is still (fluctuating up and down about 5 values).
>
> I'd like to smooth those out to get an average. I tried using
> peak, which works great for numbers going up, but not down.
>
> The mean object works, but when ramping up or down it takes those
> into the equation.
>
> Any help would be appreciated. This seems like there must be a
> very simple solution.

----
Steven M. Miller
Professor, Contemporary Music Program
College of Santa Fe

Home
SFIFEM
Atrium Sound Space
OVOS
CMP

hi jeff,
have a look at the slide object. dividing will not solve the
unsteadiness, just shift it to another level. doing additional
computation on your arduino is also not necessary, since your computer
is about 100 times faster as your arduino.
marius.

marius.

Joe Bicker wrote:
> The most reliable method I found when I experienced the same problem was
> just dividing the input in order to limit the range. There may be a better
> solution out there, but this is probably the most simple. Might also be
> worth dividing the signal at the arduino side if you want to save CPU
> cycles.
>
> On 14/03/2008, Jeff Thompson wrote:
>>
>> So I have my Arduino, running a slightly modified Arduino2Max and reading
>> the analog pins from a potentiometer. I can get the numbers into Max no
>> problem, but there's some jitter when the pot is still (fluctuating up and
>> down about 5 values).
>>
>> I'd like to smooth those out to get an average. I tried using peak, which
>> works great for numbers going up, but not down.
>>
>> The mean object works, but when ramping up or down it takes those into the
>> equation.
>>
>> Any help would be appreciated. This seems like there must be a very
>> simple solution.
>>
>> Thanks!
>>
>> Jeff
>>
>
>
> ------------------------------------------------------------------------
>

Quote: mail@jeffreythompson.org wrote on Fri, 14 March 2008 11:49
----------------------------------------------------
> So I have my Arduino, running a slightly modified Arduino2Max and reading the analog pins from a potentiometer. I can get the numbers into Max no problem, but there's some jitter when the pot is still (fluctuating up and down about 5 values).
>
> I'd like to smooth those out to get an average. I tried using peak, which works great for numbers going up, but not down.
>
> The mean object works, but when ramping up or down it takes those into the equation.
>
> Any help would be appreciated. This seems like there must be a very simple solution.
>
> Thanks!
>
> Jeff
----------------------------------------------------

I made a one-pole lowpass filter for this kind of thing. In the CNMAT MMJ Depot here:

http://cnmat.berkeley.edu/patch/4178

mz

Thanks for all the responses. I've tried the smooth object, which seems to essentially ramp numbers.

It reduces the jitter when set high enough, but then reduces the speed with which I can actually change numbers (it ramps slowly up and down).

I'm trying to think of a way to add a threshold to the smooth object, where it will perform a high level of smoothing until the change is greater than, say 8, and then it shuts off.

I can't patch it up right now, but I was thinking that perhaps some
way of changing the control input to [slide] based on the magnitude
of the difference between successive input data.

some sort of looping algorithm:

subtract current input from previous input
take absolute value
scale result to desired range
use output from scaling operation to set [slide] control
send current input through [slide] to output
store current input as previous
start loop again

That way the (presumably) small magnitude of the jitter gets filtered
but the larger magnitude 'real' input does not.

Just an idea...

On Mar 16, 2008, at 9:10 AM, Jeff Thompson wrote:

>
> Thanks for all the responses. I've tried the smooth object, which
> seems to essentially ramp numbers.
>
> It reduces the jitter when set high enough, but then reduces the
> speed with which I can actually change numbers (it ramps slowly up
> and down).
>
> I'm trying to think of a way to add a threshold to the smooth
> object, where it will perform a high level of smoothing until the
> change is greater than, say 8, and then it shuts off.

----
Steven M. Miller
Professor, Contemporary Music Program
College of Santa Fe

Home
SFIFEM
Atrium Sound Space
OVOS
CMP

Here you go Jeff. Is this what you had in mind?

Zachary

And here's a javascript way to do it.

Zachary

Here's the max patch:

save this as pathEasing.js

//Smooth out mouse movements

var mouse;
var mouseEase = 0;
var easing = 0.1;
var minDist = 0.1;

if (jsarguments.length>1)
    easing = jsarguments[1];
    minDist = jsarguments[2];

function bang()
{
    outlet(0,mouseEase);
}

function msg_float(v1)
{
    mouse = v1;
    var distance = mouse - mouseEase;

    if (Math.abs(distance) < minDist)
    {
        mouseEase += distance * easing;
    }
    else
        mouseEase = mouse;

    bang();
}

function setEasing(v) // set easing amount (0.01 will ease more than 0.9)
{
    easing = v;
}

function setMinDist(d) // set minimum distance
{
    minDist = d;
}

Thanks, Zach. Sorry - I don't know how to use the Javascript patch. Do I copy.paste it like a Max patch?

The problem with the Max one you made is that the sensitivity when making intentional transitions is still low. If I adjust the numbers quickly it still takes a while to reach the peak.

I know this is a Max forum, not an electronics one, but maybe this is a problem better solved through hardware?