# Create and Adjust VAR Model Using Longhand Syntax

This example shows how to create a three-dimensional VAR(4) model with unknown parameters using `varm` and the longhand syntax. Then, this example shows how to adjust parameters of the created model using dot notation.

Create a VAR(4) model for a three-dimensional response series. Specify that there are unknown coefficient matrices at lags 1 and 4 only.

```numseries = 3; p = 4; ar = {nan(3) nan(3)}; lags = [1 p]; Mdl = varm('AR',ar,'Lags',lags)```
```Mdl = varm with properties: Description: "3-Dimensional VAR(4) Model" SeriesNames: "Y1" "Y2" "Y3" NumSeries: 3 P: 4 Constant: [3×1 vector of NaNs] AR: {3×3 matrices} at lags [1 4] Trend: [3×1 vector of zeros] Beta: [3×0 matrix] Covariance: [3×3 matrix of NaNs] ```

`Mdl` is a `varm` model object. The properties of the model display at the command line. Observe that:

• The default value of some of the parameters are `NaN` values, which indicates their presence in the model.

• You created the model without using response data. That is, `Mdl` is agnostic about data.

Suppose that you want to add a linear time trend to the model to be estimated. By default, the linear time trend is zero. To make an unknown time trend present in the model, set the `Trend` property to a 3-by-1 vector of `NaN` values using dot notation.

`Mdl.Trend = nan(3,1)`
```Mdl = varm with properties: Description: "3-Dimensional VAR(4) Model with Linear Time Trend" SeriesNames: "Y1" "Y2" "Y3" NumSeries: 3 P: 4 Constant: [3×1 vector of NaNs] AR: {3×3 matrices} at lags [1 4] Trend: [3×1 vector of NaNs] Beta: [3×0 matrix] Covariance: [3×3 matrix of NaNs] ```