Vector length - comparison plot

Hi!

I'm trying to compare two results in a system identification procedure. My total dataset consists of 17 495 samples. I've got both the validation data set and the simulated identified data set as iddata structures. My data set is divided in half, one for identification and one for validation, and they are 8972x1x1 and 8973x1x1 in dimensions. My simulation based on the identified model is also 17 495 samples. So far, so good. Here is the problem:

To illustrate actual model fit on the validation set(left figure), I use the corresponding half-part of the simulation result(right figure, top plot) and try to compare these(note that simulation itself is done for the whole timespan, 17495). Problem is that my x-axis for these variables don't match. Left figure have x-axis 0-8793 while the right figure have 8972-17495. They are equal in length and they represent the same actual time span but the internal x-vectors don't match. The comparison plot on the left is supposed to compare against the plot on top right plot and others whcih face the same problem.

As mentioned, both data sets are iddata. Are there any way to manipulate one of them to match the other?

Cheers!