31, 1899" - whichever way is easier for you to understand. For news about the latest Excel for the web updates, visit the. Click Open in Excel and perform a regression analysis. 1, 1900 is 1 - so it stores a number that is either the number of days since "Jan. If you have the Excel desktop application, you can use the Open in Excel button to open your workbook and use either the Analysis ToolPaks Regression tool or statistical functions to perform a regression analysis there. You will also want to be careful to stick just to the region of your data - with a 6th order polynomial - if you move very far outside the range between 20 - the values of the trend line are quite likely to become quite extreme (I think, looking at your coefficients, that if you tried to plot a value for a date in 1970 - or 2050 - it would be incredibly huge, but I might have things backwards, and those values could be extremely negative numbers).Įdited to add - User777 below is correct. If you are keeping not just dates, but dates and times - the time portion is kept as a fraction of a day (so 12 noon on a particular day is stored with a number 0.5 larger than the preceding midnight). 1, 1900 - so for any remotely current dates, the number is pretty large. Linear Regression by Hand and in Excel There are two parts to this tutorial part 1 will be manually calculating the simple linear regression coefficients by hand with Excel doing some of the math and part 2 will be actually using Excel’s built-in linear regression tool for simple and multiple regression. It is - as you partially surmised - the number of days since Jan.
The value of x used to generate any point on that trend line is indeed the "very big number" that is the way Excel actually stores dates.