Detrend specified inputs/outputs

Hi,

I have a data set composed of several inputs and outputs in the form.

data = idata(Y,U,Ts)

Where Y is my outputs and U are my inputs.

I would like to use the detrend function to deterrent only some of my inputs and outputs. Others I want to leave as they are. However,

data_d = detrend(data)

detrends all my data.

Thank you for any help you can offer.

Answer 1

[Kyle Brown]

I worked out a way to do this. I'll post it case anyone has similar issues in the future.

For a time-domain data that is defined as:

data = iddata(Y,U,Ts);

Where Y and U are multiple inputs and outputs respectively. Specific inputs and outputs can be called using:

data_c(:,{'y1','y2','y4','y5','y6'},{'u1','u2','u3'})

We can then detrend the stated outputs only.

data_r = detrend(data_c(:,{'y1','y2','y4','y5','y6'},{'u1','u2','u3'}));

However, we must re-build the iddata.

Yf = [data_r.y(:,1) data_r.y(:,2) data.y(:,3) data_r.y(:,3) data_r.y(:,4) data_r.y(:,5)];
Uf = [data_r.u(:,1) data_r.u(:,2) data_r.u(:,3) data.u(:,4)];
data_f = iddata(Yf,Uf,Ts);

Note that the detrend data has changed the order of the inputs and outputs, with the numerical values following the order they were entered. You must adjust accordingly.