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logarithmic curve fittting regression
3

logarithmic curve fittting regression

logarithmic curve fittting regression

(OP)
I am referring to the regression formulas as mentioned in the HP-67 Standard Pack.   I have translated into basic language the regression formulas for Linear, Exponential and Power curve fitting and they all work alright.   However I am unable to make the Logarithmic formula work and I think there must be some mistake in the formula itself.  Can any oldtimer check, or supply another formula from another source?  (which I am unable to locate).   
I do not need the Basic program lines but just a correct formula which will work correctly for Logarithmic curve fitting.
Many thanks and I will do my best to reciprocate.
Pieropiero

RE: logarithmic curve fittting regression

Hello pieropiero,
the transformation to fit the data into a logarithmic curve works for values of independent variable where x>0 otherwise you will get an error message. Did you consider this fact?

m777182

RE: logarithmic curve fittting regression

Is it possible to see the Logarithmic formula you have?

RE: logarithmic curve fittting regression

I did the same thing with the formulas from my old HP-19C; I'll bet your problem has to do with values of x <= 0.  

Show us your input data -



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RE: logarithmic curve fittting regression

(OP)
the formula that I use can be seen at
ftp.agilent.com/pub/mpusup/pc/hbw/hbwnotes/xstats.mb

the three formulas for linear, exponential, power regression all work alright but I am unable to make the logarithmic regression formula work

the problem is definitely not with negative input.

I am not sure if I can read the formula correctly.
Can someone explain step by step to me how I can properly
proceed?   I am probably wrong in summatory handling

RE: logarithmic curve fittting regression

I tried the logarithmic formula and it worked fine for me so I presume it is your implementation of the formula not the formula itself.


RE: logarithmic curve fittting regression

could you please  repost the link?  The link to  basic program is not working.  or Could you send me that to grsuresh@hotmail.com

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