# for loop won't stop using break

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Yanxin Liu on 4 Feb 2021
Commented: Yanxin Liu on 9 May 2021
I'm using ARMA to simulate and predict a series of data. "i" represens the number of pre-sample for ARMA estimate and "j" represents the number of estimation sample for ARMA estimate.
The absolute percentage errors (APE) are calculated for different numbers of pre-sample and estimate sample data.
I want to stop the loop when the APE is small than 0.05. I used break function, but it won't stop until it finishes all the loops (till i=60, j=60)
Mdl = arima(1,0,0);
APE = zeros(60,108);
for i = 12:60
for j = i:120-i
EstMdl = estimate(Mdl,Y_out((i+1):(i+j)),'Y0',Y_out(1:i));
gasforecast = forecast(EstMdl,180-i-j,'Y0',Y_out((i+1):(i+j)));
APE(i,j) = abs(gasforecast(end)-Y_out(end))/Y_out(end);
if APE(i,j) < 0.05
break;
end
end
end

Walter Roberson on 4 Feb 2021
Mdl = arima(1,0,0);
APE = zeros(60,108);
stopping = false;
for i = 12:60
for j = i:120-i
EstMdl = estimate(Mdl,Y_out((i+1):(i+j)),'Y0',Y_out(1:i));
gasforecast = forecast(EstMdl,180-i-j,'Y0',Y_out((i+1):(i+j)));
APE(i,j) = abs(gasforecast(end)-Y_out(end))/Y_out(end);
if APE(i,j) < 0.05
stopping = true;
break;
end
end
if stopping; break; end
end
Yanxin Liu on 9 May 2021
I got it. Since I have an outter loop, the 'break' only stops the execution of the inner loop. Thank you so much.