Re: [Gnuplot-bugs] illogical error fitting polynomial

[<pl...@pi...>]

On Fri, 04 May 2007 23:36:24 +0200, Hans-Bernhard Bröker  
<HBB...@t-...> wrote:

> pl...@pi... wrote:
>
>> However if I remove the constant /10 or make it /1 or /1.0 the call to  
>> fit
>> fails saying there are not enough data points.
>
> You defined a y range, but without the division, most data points are
> outside that range.  Yes, 'fit' does respect 'set yrange'.
>
hmm, the doc for fit command says the following:

>> Ranges may be specified to temporarily limit the data which is to be  
>> fitted;any out-of-range data points are ignored.

The result of not specifying a range for fit is not explained.

Since it would be possible to inadvertantly exclude some data from a fit  
and hence produce incorrect results (eg require a fit over whole range of  
data but plot expanded detail of one region) this probably should be  
documented explicitly.

>> This is presumably a different error condition that is not getting  
>> trapped
>> correctly and displaying an incorrect error message.
>
> You presume prematurely.

Indeed I do, my appologies. Though a more explicit error message would  
help avoid confusion.

"Insufficient data points in specified range" would point the user more  
clearly to cause of the problem.

I would say "what range?" and quickly realise my mistake.


Many thanks for pointing me to the cause, it is quite possible that some  
points are still getting ignored with my /10 formular, I will expliticly  
add range parameters to fit.


Have you been able to establish whether table mode deals correctly with  
time data or not? This is holding me back in passing my data out to a  
script .

Thanks again for your help.