logarithmic curve fittting regression 3

[pieropiero]

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

 

[nbucska]

Could you pse explain what you are trying to do ?

<nbucska@pcperipherals.com>

 

[m777182]

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

 

[SteveNeely]

Is it possible to see the Logarithmic formula you have?

 

[Focht3]

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 -



Please see FAQ731-376 for great suggestions on how to make the best use of Eng-Tips Fora.

 

[pieropiero]

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

 

[fred01]

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.

 

[ganpas]

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