[Gnuplot-info] How to automatically compute root or intersection of data plots

[<lyn...@fr...>]

On 20/10/10 13:32:41, Marek W. Gutowski wrote:
> The simplest thing is to plot whatever is of interest and then
> to use mouse for zooming the area in question. Read current
> mouse pointer coordinates in the lower left part of plot.
> Zoom again, if still not satisfied.

Thanks  Marek  for  Your  answer. I seem to have asked it a bit unpresize. I'd
need  an         automatic/computational  evaluation  where  two  data   plots
intersect or where the difference of the two has its roots. Reading it off the
plot is OK for a few plots but if You need   to evalutate a big load  of  data
it would be nice to have a program doing that for You.

Can that be done with gnuplot or any other linux tool?

Thanks for any help or hints.
Lynx

> lyn...@fr... wrote:
>> Is  there  a  possibility  to  determin  the  root  of  a  data  plot  or  the
>> intersections of two plots depending on the interpolation type that was chosen
>> for plotting? Is that possible with gnuplot or another free linux tool?
>> I know it is tricky to define the intersection points for data plots since the
>> intersection mostly depends on the interpolation type and is rarly exactly  on
>> a  data  point.  Still it is often necessary to estimate the intersection of a
>> data plot with another or with a function.
>> It would be already helpful to know the two data points in between  which  the
>> intersection  would  lie.  I  guess  for  the  problem  of  finding  the  root
>> (intersection of a plot with the x-axis) it would just be a problem of finding
>> the pairs of adjacent points where thy y-value chages sign.
>> Any  way to  do that with gnuplot or another tool? Still, having an evaluation
>> possibility depending on the gnuplot interpolation type (eg.  straigth  lines,
>> splines or kdensity) would be great.
>>
>> Thanks for any help or hints about this.
>> Lynx
>
> -- 
> Marek W. Gutowski
> Institute of Physics PAS, ON-3.2, Al. Lotnikow 32/46
> 02-668 Warszawa, Poland, tel. +48-22-0228436601 ext. 3122
> == To talk or not to talk?  Yes, talk, plain ASCII please ==
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~