Filter Question

I am trying to use a filter to get rid of noise on some data that I have. However, this data continuously updates. I can run a simple test in the command window and the code works fine:

for i=1:30
  num(i)=rand;
end
a = 1;
b = [1/4 1/4 1/4 1/4];
y=filter(b,a,num);
plot(y)

However, when i try to implement this into my program that reads data from the serial port, I get the following error:

??? In an assignment A(I) = B, the number of elements in B and I must be the same.

Note that when this is implemented into my code, the variable num is now a continuously updating value.

How could I get around this error?

[Honglei Chen]

Could you post your code snippet and let us know which line errors out?

Answer 1

[Wayne King]

Do you have a variable in your workspace called filter?

If you enter

>>which filter

is it a variable?

If so, clear that variable.

The code you posted should work, but there is no reason to form num using a for loop.

num = rand(30,1);
a = 1;
b = [1/4 1/4 1/4 1/4];
y=filter(b,a,num);
plot(y)