G Guest Mar 13, 2007 #1 I can use the "forecast" formula to find a Y value given an X, but not the other way around. please help! thanks
I can use the "forecast" formula to find a Y value given an X, but not the other way around. please help! thanks
D David Biddulph Mar 13, 2007 #2 Can't you just reverse the order in which you give the second and third arguments of the FORECAST() function? In other words, instead of =FORECAST(x,known_y's,known_x's), use =FORECAST(y,known_x's,known_y's) ?
Can't you just reverse the order in which you give the second and third arguments of the FORECAST() function? In other words, instead of =FORECAST(x,known_y's,known_x's), use =FORECAST(y,known_x's,known_y's) ?
M Mike Middleton Mar 14, 2007 #3 jmi - Behind the scenes, FORECAST uses the least-squares method for fitting a simple linear function. So, instead of using FORECAST, use the SLOPE and INTERCEPT worksheet functions. Since Y = Intercept + Slope*X, a little algebra indicates X = (Y - Intercept)/Slope. - Mike http://www.mikemiddleton.com
jmi - Behind the scenes, FORECAST uses the least-squares method for fitting a simple linear function. So, instead of using FORECAST, use the SLOPE and INTERCEPT worksheet functions. Since Y = Intercept + Slope*X, a little algebra indicates X = (Y - Intercept)/Slope. - Mike http://www.mikemiddleton.com
