HP Forum Archive 21

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Help with creating residual plot Message #1 Posted by Phillip B. on 9 Oct 2012, 4:29 a.m. Hello! I searched the internet high and low, but I could not find any information how to create a residual plot after you run the linear regression. It is simple on a TI calculator used as an example in my class, but I am clueless on how to do the same on my HP50g. When I attempt to create a list of residual by entering "L2-Y1(L1)" it creates an error because "Y1(L1)" creates a list with one additional number that I am not sure where is coming from. But, yes, I am very clueless on how to do this. Hope you all can help, Phillip

Re: Help with creating residual plot Message #2 Posted by Andrew Feist on 10 Oct 2012, 12:49 p.m., in response to message #1 by Phillip B. I've got a 48gII, not a 50, but my understanding is that it's similar enough to be getting on with. The question then becomes: how are you creating your L1, your L2, and your Y1? A bit of playing around shows that if I have something like '.505+1.475*X' stored into Y1, if I then execute Y1 on a list L1 (in either RPN or alg mode) I get a result list whose first element is .505 and the other elements are 1.475 times the elements of L1. If I write Y1 instead using "ADD" instead of + (in RPN, << 1.475 * .505 ADD>>; probably something similar in alg) then it works as expected. Also, if I rewrite the equation to '1.475*X-(-.505)' it works as expected. It looks like + is the only operator that doesn't act on each member of a list, which seems a little annoying.

Re: Help with creating residual plot Message #3 Posted by Gilles Carpentier on 10 Oct 2012, 2:35 p.m., in response to message #1 by Phillip B. Hi I don't undersstand what are L1 and L2 here... Perhaps one way is a small program considering that: - The stat matrix is \GSDAT (SigmaDAT) - The predicted value given with the PREDV command And add a new column in the stat matrix with mesured vaue minus expected value Are you in RPL mode ? Example : � \GSDAT DUP �->COL DROP SWAP � PREDV � MAP - 3 COL+ � [[ 1. 10. ] [ 2. 23. ] [ 3. 29. ]] -> '1.66666666667+9.5*X' [[ 1. 10. -1.1666666667 ] [ 2. 23. 2.3333333333 ] [ 3. 29. -1.1666666667 ]] Then you can draw the plot Edited: 10 Oct 2012, 2:39 p.m.

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