HP 48G Linear Regression Best Fit Line

[Rodger Rosenbaum]

(12-23-2021 12:41 PM)MNH Wrote:  

(12-23-2021 04:13 AM)Rodger Rosenbaum Wrote:  The HP48 and descendants come through again! I'm glad it all worked out--you'll be the envy of the other guys you work with. :-)

My next step is to get a direction on the best fit line. I've been scanning the Internet for this. It looks like I'll need to know where the x and y-intercepts are in order to get a delta x and a delta y. I can then use tan^-1(delta x / delta y) to calculate the azimuth of the line.

When you execute ORTH the first number (.008321172 for the data we've been testing with) is the slope. The angle the line makes with the x axis is just the atan of the slope. Is your "azimuth" the angle with the y axis? In that case simply calculate atan(1/slope).

(12-23-2021 12:41 PM)MNH Wrote:  I have a question unrelated to the above. What does the data on stack level 3 mean? The data is placed on the stack after selecting right-shift, STAT, Fit data..., Linear Fit.

3: '672.34932+0.00832...
2: Correlation: 0.893...
1: Covariance:
94.09017

What's the purpose of the single quotation mark to the left of the first digit on stack level 3? If you view (right-shift, STACK) the data appears as 672.34932+0.00832X.

It's because that thing on the stack is an algebraic object (its type = 9).