how to contaminate ecg signal with noise

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sai lakshmi 2019-11-16

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https://ww2.mathworks.cn/matlabcentral/answers/491398-how-to-contaminate-ecg-signal-with-noise

评论： Daniel M 2019-11-23

I am working on the project namely "FALSE ALARM REDUCTION IN ATRIAL FIBRILLATION DETCTION USING DEEP BELIEF NETWORKS".

In this i need to download two databases, namely 07910m.mat{MIT_BIH ATRIAL FIBRILLATION DATABASE} which is attached here,and also the 'em' recording {MIT_BIH NOISE STRESS TEST DATABASE} is attached.

The afib database has Fs=250Hz and 10h in length,and 'em' recording is 30 min and has Fs=360Hz

now i need to make the 'em' recording 10h in length

in the paper its told that i can be done using auto regressive model,iam not knowing how to do it

can anyone suggest me the coding for this

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Daniel M 2019-11-20

Well you know there will be a loop involved. Can you show me the code you currently have? I can help you get there.

sai lakshmi 2019-11-20

load('07910m.mat');

x1=(val(1,:))/200;

n=length(x1);

fs=250;

t=0:1/fs:(n-1)/fs;

%plot(t,x1);

%[qrs_amp_raw,qrs_i_raw,delay]=pan_tompkin(x1,fs,0);

load('emm.mat');

x2=(val(1,:));

Fs=360;

x3=resample(x2,25,36);

figure(1);

subplot(2,1,1);

plot(x2);

subplot(2,1,2);

plot(x3);

[d1,p1,rc] = aryule(x3,20);

for c=1:20

psi(c)=d1(c+1);

end

zmwn=randn(size(x1));

z=double.empty(0,1000000);

for i=1:length(x1)

z(i)=(-1.8909*z(i-1)+1.2973*z(i-2)-0.7229*z(i-3)+0.4524*z(i-4)-0.2636*z(i-5)+0.2620*z(i-6)-0.2307*z(i-7)+0.2164*z(i-8)-0.8175*z(i-9)+0.1536*z(i-10)-0.1285*z(i-11)+0.0878*z(i-12)-0.0736*z(i-13)+0.0682*z(i-14)-0.0679*z(i-15)+0.0487*z(i-16)-0.0268*z(i-17)+0.0249*z(i-18)-0.0153*z(i-19)+0.0026*z(i-20))+zmwn(b);

end

I am getting an error "subscript indices must be either of positive values or logicals"

I understood the occurence for error,but am not recognizing of how to simulate the noise signal in this.

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回答（2 个）

Daniel M 2019-11-20

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https://ww2.mathworks.cn/matlabcentral/answers/491398-how-to-contaminate-ecg-signal-with-noise#answer_402488

编辑：Daniel M 2019-11-21

I obviously cannot run this code because I don't have the data nor any of the associated functions. By the way, you are getting an error because you are trying to access z at negative index locations.

Here is an example of how you would plot the equation. Keep in mind the assumptions I've made, which I've tried to comment.

clearvars
clc
sz = [1 1000];
e = randn(sz); % epsilon
X = nan(sz); % preallocate 
X(1) = 0; % set first value. Don't know what this should be.
c = 1; % a constant, don't know what this should be
p = 5; % set the order of the model. Don't know what this should be.
% note that p cannot be greater than the iterating variable of the loop
% otherwise, it would try to access negative index locations
% So, either initialize your loop index at a value greater than 2 (and have the starting values of X)
% or do it this way, using increasing values of p, up to n-1
phi = rand(1,p); % your values of phi
for n = 2:sz(2)
    ii = 1:min(p,n-1); % see the note above
    
    sigma = dot(phi(ii), X(n-ii)); % sum of the products of the elements
    X(n) = c + sigma + e(n);
end