Re: fit(timedata)

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

On Mon, 25 Feb 2008 14:46:56 +0100, <pl...@pi...> wrote:

sorry , posted without checking what I wrote...
> Hi,
>
> I have some time data plotting correctly and need to fit a straight line.
> This seems fine but when I
>
> set timefmt "%H:%M:%S"
> set xdata time
>
> ...
>
> plot fit(x)

c=3;m=-1;
f(x)=x*m+c;
fit f(x) datafile using 1:4 via m,c;

plot datafile  using 1:(($4)/1.0) w l title "resampled DAC output"\
, f(x) with lines title "lin. regression fit"  \
  ;

this gives me a flat line at 1.5 instead of a neg slope from 3.0 If I skip  
the fit call it gives me a flat line at -60000 (appx)

:?


>
> I get y values indicating that it is using integer seconds for x and not
> respecting the xdata setting.
>
> I suppose I could work around it by setting a constant to subtract but
> should this be needed.
>
> The current behaviour seems a bit inconsistant unless I'm mususing it.
>
> Thx, Peter.
>
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