Open adburnham opened 1 year ago
I agree- you aren't missing anything the values don't show up (although it is inferred that this was coming in version 10.1 or 10.2 - I tried those just in case it appeared then disappeared but no dice). As for the values being different, I believe this is related to slightly different calculations used within squid2.5 for the slope/Expo calculation than just RobReg. I'd have to go through some of the documentation to confirm this though. I'll have a quick look through and see if I can point you to a specific spot that explains this.
I don't see the problem. Please provide an example.
v1.10.4, demo project:
value of slope and intercept given, but not uncertainties. Are they somewhere else?
On the left window.
Those are the errors of the individual datapoints being regressed. Looking for something like what is shown in the "expo" expression:
But in cases where the RobReg is using other X-Y parameters.
I guess in theory you could make a custom expression with the stuff you are plotting in "Plot any two" using the RobReg and get the values from there @adburnham although that doesn't address the discrepancies based on what regression algorithm is being used. See issues #696 and #617 for some context
Well, I mis-understood issue #709 originally and addressed it by providing the point-wise uncertainties in the left hand details. Now I understand what is wanted.
History: The plot-any-two functionality uses an algorithm developed by @noahmclean and implemented at https://github.com/CIRDLES/McLeanRegression. The corresponding paper is here.
The uncertainty is represented by the envelope, which has a plus/minus value at each x. The original matlab code is here.
The outputs are described there as:
'a' is the point on the line with first component a1 specified above
'a2s' contains the two-sigma uncertainties in the free components of a
'v' is the direction vector of the line with first component v1 as input
'v2s' contains the two-sigma uncertainties in the free components of v
'Sav' contains the covariance matrix for the free components of a and v
'MSWD' is the mean of the squared weighted deviates (reduced chi-square)
'n' is the number of analyses included in the calculation, = sum(skipv)
Please review and decide how you want to proceed. If you want a simple vanilla regression, then that should become an issue asking for that alternative. Hopefully, @noahmclean will chime in.
Cheers
This error arose as I was writing up the results section of a report. Because there is a range of opinions about the best fit slope (some researchers finding 1.7 better than the previously preferred value of 2.0) I thought it would be good to report what I found. I think it would be good to have consistency between the Expo value used for calculations and the slope calculated by Plot Any Two Expressions.
Following up on #709 - though not in relation to the rejected points issue, but rather the way it calculates uncertainties on the slope and y-intercept. Different parts of SQUID seem to give different values (as outlined below), and also I thought you said in #709 that an update meant that Plot Any Two Expressions would give uncertainties.
Maybe I'm missing something, but although I can see the error envelope for the best fit of any two expressions (blue dotted line), the window only shows (written out) the values of the slope and y-intercept but not their uncertainties. Is there any way to find out the uncertainties, short of sending the values to Excel and calculating in Isoplot? I tried viewing it in "Manage expressions", where I can see the calculation of Expo, but the numbers in the Peek window don't match up to to what is calculated in "Plot Any Two Expressions".