how to do implement difference equation in matlab

122 次查看（过去 30 天）

moonman 2011-11-14

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/21192-how-to-do-implement-difference-equation-in-matlab

评论： Daniel 2024-3-27

Hi i am stuck with this question

Write a MATLAB program to simulate the following difference equation 8y[n] - 2y[n-1] - y[n-2] = x[n] + x[n-1] for an input, x[n] = 2n u[n] and initial conditions: y[-1] = 0 and y[0] = 1

(a) Find values of x[n], the input signal and y[n], the output signal and plot these signals over the range, -1 = n = 10.

The book has told to user filter command or filtic

my code is down kindly guide me about initial conditions

5 个评论
显示 3更早的评论隐藏 3更早的评论

Fangjun Jiang 2011-11-15

编辑：Walter Roberson 2021-3-5

My advice:

2. Use proper punctuation mark, e.g. comma, period, question mark.

3. Read your own question again after posting, e.g. what is x[n] = 2n u[n]?

4. Update your question with comments, not answers.

Ahmed ElTahan 2016-3-25

编辑：Ahmed ElTahan 2016-3-25

Here is a function I have built to calculate it with added example. https://www.mathworks.com/matlabcentral/fileexchange/56142-output-estimation-difference-equation

请先登录，再进行评论。

请先登录，再回答此问题。

回答（3 个）

Honglei Chen 2011-11-14

2
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/21192-how-to-do-implement-difference-equation-in-matlab#answer_27923

在 MATLAB Online 中打开

I think your b is incorrect, it should be [1 1] instead. To accommodate for the initial value of y and x, you need to translate them into the corresponding filter state. filter command is an implementation of direct form II transpose, so you can use filtic to convert y and x to the state.

Here is an example, where n runs from 1 to 10. Based on you example, x[0] is 1.

n = 1:10;
a = [8 -2 -1];
b = [1 1];
yi = [1 0];
xi = 1;
zi = filtic(b,a,yi,xi)
y = filter(b,a,2.^n,zi)

BTW, I doubt if the input is really 2.^n as this becomes unbounded very quickly. Are you sure it's not 2.^(-n)?

HTH

8 个评论
显示 6更早的评论隐藏 6更早的评论

Divya K M 2020-5-9

移动：DGM 2023-2-26

output of difference equation should be discrete but the output waveform is coming continuous

Aditya Kumar Singh 2020-11-17

移动：DGM 2023-2-26

use stem instead of plot... you should get the correct waveform after that

请先登录，再进行评论。

Mohazam Awan 2017-10-10

2
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/21192-how-to-do-implement-difference-equation-in-matlab#answer_285091

在 MATLAB Online 中打开

%%DSP LAb Task 4
% Difference equation implementation in matlab
%
clc
clear all
close all
% using filter function
n=-5:1:10;
index=find(n==0);
x=zeros(1,length(n));
x(index)=1;
subplot(2,2,1)
stem(n,x)
grid on 
axis tight
b=[1 0];
a=[1 -2];
y=filter(b,a,x);
subplot(2,2,2)
stem(n,y,'filled','r')
grid on 
axis tight
% Now without filter function
y1=zeros(1,length(n));
for i=1:length(n)
    if(n(i)<0)
        y1(i)=0;
    end
    if (n(i)>=0)
        y1(i)=2*y1(i-1)+x(i);
    end
end
subplot(2,2,3)
stem(n,y1,'filled','k')
grid on 
axis tight

2 个评论
显示无隐藏无

Divya K M 2020-5-9

Is this code for given question if so means can I explain

Daniel 2024-3-27

Why do you use negative samples in the n vector? I am trying to use only positve samples and it doesnt work

请先登录，再进行评论。

Fangjun Jiang 2011-11-14

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/21192-how-to-do-implement-difference-equation-in-matlab#answer_27915

It might be a filter. But I thought all the assignment was asking you to do is to write a for-loop to generate the y series data based on the equation and the initial conditions.