smooth function on long array

Hello, i am writing a program that plots some data from serial port. i need to smooth data collected because it's noisy (i get it from 4 temperature sensors). the problem is that the program must run for several hours without freeze and get a new values of the four temperatures in about 3 seconds. When the program has collected something like 500 samples per temperature, it starts to become very laggy and at 7-800 samples it freezes. this because i run the smooth function with span of 101 samples every loop. how can i get a continuous function (as if i did a smooth on all the array) without doing it every loop? there is a workaround for my problem? thanks for answers alberto

[Jan]

Without seeing the code, we cannot guess what you are doing or what's going wrong. What exactly is "laggy"? What are "7-800 samples"? Your code freezes, when you have 7 samples and run a smoothing function over 101 samples? Does this mean, that the smoothing function has a bug?

Please post relevant details - by editing the question, not as comment.

[Walter Roberson]

If you post your smoothing function then we might be able to tell you how to run it without having the full previous input.

Answer 1

[Walter Roberson]

It sounds like you are not pre-allocated your arrays, so as your program runs the code gets slower and slower spending all of its time growing the arrays. You should allocate memory in advance to store a reasonable number of points, and if you detect that you are collecting more points than expected, you should grow the array by chunks rather than one-at-a-time. For example,

growby = 64;
curlen = 256;

v1 = zeros(curlen,1);
v2 = zeros(curlen,2);

maxsamp = 10000;   %fail-safe, if we reach this the termination was missed

end_signaled = false;

for sampnum = 1 : maxsamp
  end_signaled = check_for_end();  %external trigger to shut down?
  if end_signaled
    break;
  end
  if sampnum > curlen
    curlen = curlen + growby;
    v1(curlen) = 0;   %extend the array by writing past the end of it
    v2(curlen) = 0;   %extend the array by writing past the end of it
  end
  ...
  v1(sampnum) = ....
  v2(sampnum) = ....
end

%when we get here then if end_signaled is true we got a clean shutdown
%and otherwise it was because we reached our hard limit