title: R-ARIMA parameters. How to determine arima (p,d,q) parameters?
body: <p>I have weekly data values extracted from google trends and I want to apply time series in R for predicting future values. I have tried using auto.arima() but the results seem to be only one constant value for all future prediction, and if i manually give random parameters in arima(c(p,d,q)), I am getting various types of results. So how to determine appropriate values for my data.</p>
  
  <pre><code>data2&lt;-ts(data$Volume)
  [1]  64  74  64  68 100  87  79  72  66  74  58  68  65  71  71  71  63  65 62  58  58
  [22]  58  58  60  56  51  56  52  58  59  58  60  66  67  69  67  80  66  73  73  72  68
  [43]  66  70  69  66  68  67  60  50  36  50
  fit&lt;-auto.arima(data2)
  pred&lt;-predict(fit,n.ahead=30, interaval="prediction", se.fit="FALSE") 
  plot(pred)
  pred
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/lxJMY.jpg" alt="enter image description here"></p>
  
  <pre><code>fit&lt;-arima(data2,c(3,1,1)
  pred&lt;-predict(fit,n.ahead=30, interaval="prediction", se.fit="FALSE") 
  plot(pred)
  pred
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/9TKZS.jpg" alt="enter image description here"></p>