how to replace all negative values from an iddata with zero?

Hello Matlab community! I have an iddata with predicted values from an ARMAX model, for the analysis, I want to replace all negative values with zero, and then plot the result of measured vs predicted in the same graph, how can I do that? I tried to subtract the output values yp.y, been yp the iddata with the predicted values, and then set the negatives values to zero y(y<0)=0, and again construct the iddata yp1 = iddata(y,[],5,'TimeUnit','minutes) but then I realized the zero values are still there and the plot of measured vs predicted is done separately. so I wanna know if there is a way to replace the negative values with zero without extracting the output vector out of the iddata format. thanks

Answer 1

[Elizabeth Reese]

I was working based on the example here in the predict documentation.

This example creates a data iddata object of measured outputs and a yp iddata object of predicted outputs.

If I want to change the data inside the yp object, I can do that using:

 yp.OutputData

So, to change all of the negatives values in yp to 0, I would do:

 yp.OutputData(yp.OutputData < 0) = 0;

If you want to do this for data, you can as well. Then, I could plot the data and yp against each other using:

 plot(data,yp);
 legend('Estimation data','Predicted data');