The difference between filter,conv in MATLAB the principle of communication

Conv is to do convolution, that is, according to the practice of the book, first Flip, in a step-by-step translation, to obtain results. For a sequence of two lengths of n,m, the convolution result length is m+n-1

Filter is to do the filter, in fact, the principle and convolution is figured out, but the method of processing the results are different, first look at the sample program:

x=[1,2,3,4,5];
h=[1,1,1];

Y1=conv (h,x)
y2=filter (h,1,x) y3=filter (x,1,h) y4=filter (X,1,[h,zeros
(1,4)))

The results are:

Y1 =

     1     3     6     9     9     5


y2 = 1 3 6 9


y3 =

     1     3     6


y4 =

     1     3     6     9 of 9 5

The results are now explained;

1.y1 is indeed calculated strictly according to the mathematical expression of convolution, not explained.

In explaining the following several, first say the use of filter: Filter (b,a,x), where b,a form a difference equation, X is the input signal, for example:

Filter ([1,2],1,[1,2,3,4,5]) implements Y[K]=X[K]+2*X[K-1]
What we are talking about here is the situation of a=1. With the basic description, now to the main:

2. The filter function translates to stagnation at x's last input with the filter's first coefficient pair to align. Here for

From

				1	1	1 5, 4 3 2 1
Output 1,
				to	1	1 + 1 5 4 3 2 1
Output 12

3. To verify the 2 point of view, here is:

From

		1	2	3 4, 5 1 1 1
Output 1, to 1 2,	3 4 5 1 1	1
Output 6

4. Still the view of validating 2, from

				1 2 3 4-5 0 0 0 0 1 1 1 1
output 1, to
				1	2	3	4	5
				0	0	0	0 1
1 1 1 output 5	

And, in the 4th case, by filling 0, all 1 are moved to the end of the filter tap, and the result is the same as the convolution.

Here, I think we can understand the difference and relationship between the two.