title: Getting an error "'xreg' and 'newxreg' have different numbers of columns"
body: <p>I just started with R and time series forecasting.
  I am doing forecasting for 1 variable (consumption) and one exogenous variable (income). This is quarterly data.
  When I ran the model with R code,</p>
  
  <pre><code>    #train_exp &lt;- exp_trial[,1][1:150]    
      #train_inc &lt;- exp_trial[,2][1:150]    
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/kgupm.png" alt="enter image description here"></p>
  
  <pre><code>    model_train_exp &lt;- arima(train_exp,order = c(0,2,6),seasonal = list(order=c(0,1,1),period = 4), xreg = train_inc)    
  </code></pre>
  
  <p>this model has no errors. but, when I forecast it, i get an error <strong>xreg' and 'newxreg' have different numbers of columns</strong></p>
  
  <pre><code>    forcasted_arima &lt;- forecast.Arima(model_train_exp, h=14)    
  </code></pre>
  
  <p>there are so many arguments for forecast.arima. I am not familiar with those.
  Can someone please tell me what should be the code for it?</p>