FORECAST formula needed

Question

I have this spreadsheet with some data in column A - Date, column B (keyword usage on a specific date in 2012) and in column C (keyword usage on a specific date in 2013), as it is shown on picture:

What I would like is a function like FORECAST which would "predict" the value for the future date, in this case for February 22 (C5), based on this data.

Can you please help me with the formula?

Answer 1

You can use the =FORECAST(value, data_Y, data_X) formula.

value is the known value for which you want to predict the corresponding forecast (in your case B5);
data_Y is the series of data points for which you want to predict the future value (C2:C4);
data_X is the series of corresponding data points which form the basis of the forecast (B2:B4).

So in your example the formula you would put in C5 is =forecast(B5,C2:C4,B2:B4) which will return 28.7

You can find all formulas and their explanations for Google Spreadsheet at https://support.google.com/drive/bin/static.py?hl=en&topic=25273&page=table.cs