# Calculate area from a signal

8 vues (au cours des 30 derniers jours)
Julio Martín le 10 Fév 2022
Modifié(e) : Julio Martín le 13 Fév 2022
Hi, would like to calculate area from this emg signal
There are three different channels. I've done RMS and snap the exact tiem I need to analyse but don't know how to calculate total area
My code is:
for c=2:2
A=strcat('S1_',num2str(c));
B=strcat(A,'.emt');
D=importdata(B,'\t',12);
[F, C]=size(D.data);
x=filter(Filtro_emg,D.data);
centro=(F-mod(F,2))/2;
x=x(((centro-4000)+242:(centro-4000)+3026),:);
RMS = Rms_emg (x,100)*1000;
S=smoothdata(RMS);
plot(S);
for b=3:5
Areatotal(b,c)=sum(S(:,b)); I've tried with this, but don't know if it's correct
Media(b,c)=mean(S(:,b));
Maximo(b,c)=max(S(:,b));
end
end
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### Réponse acceptée

AndresVar le 10 Fév 2022
Modifié(e) : AndresVar le 10 Fév 2022
area = trapz(x,y) % i think for you trapz(S(:,b)) or just trapz(S(:,b)) if dx = 1
sum also works so you can compare your result. You must multiply the sum by dx, but it looks like dx=1 in your case.
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AndresVar le 12 Fév 2022
Modifié(e) : AndresVar le 12 Fév 2022
for integral signal use 'cumtrapz' or 'cumsum'
btw beware of units when integrating and finding area. make sure its what you expected. dx is 1 but if you want to integrate with respect to time you need to find what is dt.
Julio Martín le 13 Fév 2022
Modifié(e) : Julio Martín le 13 Fév 2022
Thank you. Exactly I have doubs about the result
With this code
for c=2:2
A=strcat('S1_',num2str(c));
B=strcat(A,'.emt');
D=importdata(B,'\t',12);
[F, C]=size(D.data);
x=filter(Filtro_emg,D.data);
centro=(F-mod(F,2))/2;
x=x((centro-4000)+133:(centro-4000)+483,:);
RMS = Rms_emg (x,100)*1000;
S=smoothdata(RMS);
figure
for b=3:3
plot(S(:,b));title('Tibial anterior');grid;xlabel('Tiempo mseg');ylabel('uV');
AreaGM1=sum(S(:,b));
end
end
I have a result of 42756.251 uV (I supose it's impossible in a time of 350 miliseconds). If x is time in miliseconds, how could I calculate it?
Thank you so much

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