forecast future output of a defined model

Hi,

I'm have input-output data and I'm using an armax model to forecast the production in the future. The time-series is for 58 months.

y=outputdata;

y2=inputdata;

% the model is:

sys=armax([y y2 ones(length(y),1)],[1 1 1 0 0 0])

sys =

Discrete-time ARX model: A(z)y(t) = B(z)u(t) + e(t)

A(z) = 1 - 0.3582 z^-1

B1(z) = 0.3051

B2(z) = 276.9

Sample time: 1 seconds

Parameterization:

Polynomial orders: na=1 nb=[1 1] nk=[0 0]

Number of free coefficients: 3

Use "polydata", "getpvec", "getcov" for parameters and their uncertainties.

Status:

Estimated using ARMAX on time domain data.

Fit to estimation data: -2.193% (prediction focus)

FPE: 5708, MSE: 5147

Now I want to forecast the production for the next two months. I'm using the following:

K=2;

yf=forecast(sys,y,K)

but I get this error:

Error using idmodel/forecast (line 101)

The number of inputs and outputs of the model must match that of the data.

Any ideas where the error might be?

Thanks!