I have past 1 year of sales data and now i want to predict sales for next coming year. How can i predict it.
You can not predict sales for the whole next year by training your model with only one year data.
But still one year data is better than having nothing. And you can analyze one year data to find trends and patterns. On top of those trends and patterns, you can apply domain knowledge and make some very some useful strategic decisions.
Problem you are trying to solve is called Time Series Forecasting as temporal order of input matters while training.
Here are reference points you can your start with :
You can also try random walk models with confidence intervals. The idea of random walk process is it tries to simulate what might be your next point based on your current point. Random walk models are of many types, particularly in retail (sales data) you usually come across 2 types:
- random walk with drift (drift will be an upward or downward trend in your data)
- random walk without drift
The forecast package in R offers an excellent method auto.arima that you can use to implement this technique. If auto.arima is not able to fit an ARIMA model on your data it usually fits an ARIMA(0,1,0) which is tantamount to random walk.
I recommend using Facebook’s open source tool for forecasting named “Prophet”: https://facebook.github.io/prophet/docs/quick_start.html