The Excel Slope Function uses the following equation to calculate the intercept of the linear regression line through a set of given points:
where the slope, b is given by the equation:
and the values of x and y are the sample means (the averages) of the known_x's and the known_y's.
The Excel Intercept function calculates the intercept (the value at the intersection of the y axis) of the linear regression line through a supplied set of x and y values.
The syntax of the function is:
Where the arguments are:
known_y's    The array known yvalues. 
known_x's    The array of known xvalues. Note that the length of the known_x's array should be the same length as known_y's, and the variance of the known_x's must not be zero. 
The spreadsheet below shows an example of the Excel Intercept function used to calculate the point at which the linear regression line through the known_x's and known_y's (listed in cells F2:F7 and G2:G7) intersects the yaxis.
The known_x's and known_y's are plotted on the chart in the spreadsheet.
As shown in cell F9 of the spreadsheet, the call to the Intercept function is:
which gives the result 2.4.
Further examples of the Excel Intercept function are provided on the Microsoft Office website
If you get an error from the Excel Intercept function, this is likely to be one of the following:
#N/A    Occurs if the supplied known_x's and known_y's arrays are of different lengths. 
#DIV/0!    Occurs if either:
