Need some matlab help adding sequences

[kevinf]

Homework Statement

The problem provides a sequence. Let x(n) ={1,-2,4,6,-5,8,10} where x(-4)=1, x(-3)=-2,etc.
Generate x1(n) = 3x(n+2)+x(n+4)-2x(n)

The Attempt at a Solution

x = [0, 0, 1, -2, 4, 6, -5, 8, 10, 0, 0, 0, 0];
n = -6:6;

x1 = x * 3;
n1 = n-2;

x2 = x * 2;
n2 = n;

x3 = x;
n3 = n+4;
subplot(4,1,1), stem(n1,x1)
grid on
subplot(4,1,2), stem(n2,x2)
grid on
subplot(4,1,3), stem(n3,x3)
grid on

The above is the code I have so far to try to get each of the terms separately. but the difficult part is how to add these sequences together, since they start at different indices. I've tried some for loops but i can't figure out a way to get it to sweep the indices and compare them correctly. any help?? thanks

 

[KataKoniK]

Hi there,

Thank you for sharing your code. It looks like you are on the right track. The key to adding the sequences together is to make sure they are all the same length. In your code, you have already padded the original sequence x(n) with zeros so that it is the same length as the other sequences. Now, you just need to shift the indices of x(n) so that they start at the same index as the other sequences.

Here is one way to do it:

1. Create a new vector n4 that starts at -6 and goes to 6, just like n. This will be the new index for your final sequence.

2. Shift the indices of x(n) by adding 6 to each index. This will make the indices go from 0 to 12, just like n4.

3. Add all the sequences together: x1(n)+x2(n)+x3(n)+x4(n). This will give you your final sequence.

Hope this helps! Let me know if you have any other questions.