Re: [Gnuplot-info] How to fit a line in log plot or how to help converge exp better

[Thomas S. <t.s...@fz...>]

> And what would be the most elegant way to cope with the titels containing
> the fit parameters? The first file below is what I want but done clumsy.
> After that comes
> my reread attempt I got stuck on. How should I handel the third  case the
> line of which
> is missing?

use this as 'dosis_single_fit.gpl':

c_p= c_p + 1
c_l= c_p + 2
set yrange [-27.63:-16.22]
fit log(a)-b*x '< sed "s/ 0/  ?0/g" dosis.dat' using 1:(log(column(c_l)))
via a, b
set key left at graph 0.5, graph 1.0-c_p*0.1
set yrange [1e-12:9e-8]
ptitle(a,b) = sprintf("%e * exp(-x*%e)",a,b)
plot '< sed "s/ 0/ ?0/g" dosis.dat' using 1:c_l t "C_2: $c_p" ls c_p with
lp,  a * exp (-x*b) title ptitle(a,b) lt c_p
if (c_p < 4) reread

you need to adjust the factor in 'set key...' a little bit, and the format
string inside the 'sprintf' function.


lynx.abraxas wrote:
> 
> On 27/08/07 03:40:51, Thomas Sefzick wrote:
>> 
>> > gnuplot> load 'dosis_spz_fit.gpl'
>> >         No data to fit
>> 
>> with the data and the script you provide i'm not able to reproduce your
>> problem.
>> i'm using gnuplot 4.0 and gnuplot 4.3.
>> in both versions the fit converges after 10 iterations:
>> 
>> http://www.nabble.com/file/p12344733/fit.log fit.log 
>> http://www.nabble.com/file/p12344733/dosis.gif 
>>
> I figured out that my "set yrange [1e-12:9e-8]" before the fit causes the
> error. Is it in
> intended that yrange effects fit?
> The only thing left now is how to get the multiplot have nice axes; with
> reread they get
> overpainted. And what would be the most elegant way to cope with the
> titels containing
> the fit parameters? The first file below is what I want but done clumsy.
> After that comes
> my reread attempt I got stuck on. How should I handel the third  case the
> line of which
> is missing?
> 
> Thanks a lot for Your help
> Lynx
> 
> ________________________________________________
> 
> set output "Dosis.png"
> set style line 1 lt 1 lw 2
> set style line 2 lt 2 lw 2
> set style line 3 lt 3 lw 2
> set style line 4 lt 4 lw 2
> #set terminal png font FreeSans 14 crop size 700,500
> set xrange [1:12]
> set xtics 1,1,11
> set label 1 'Spz' at graph 0.97, graph -.05
> set mytics 10
> set label 2 'I[A]' at graph -0.05, graph 0.99
> set key right top # Left reverse
> set termoption enhanced
> a= 5e-8
> c= 5e-8
> e= 5e-8
> f= .8
> g= 5e-8
> b= .7
> FIT_LIMIT = 1e-9
> FIT_MAXITER = 0
> set log y
> titel(s,n,t,m) = sprintf("%s= %.1e; %s= %.1e", s, n, t, m)
> fit log(a)-b*x '< sed "s/ 0/  ?0/g" dosis.dat' using 1:(log($3)) via a, b
> fit log(c)-d*x '< sed "s/ 0/  ?0/g" dosis.dat' using 1:(log($4)) via c, d
> fit log(e)-f*x '< sed "s/ 0/  ?0/g" dosis.dat' using 1:(log($5)) via e, f
> fit log(g)-h*x '< sed "s/ 0/  ?0/g" dosis.dat' using 1:(log($6)) via g, h
> set yrange [1e-12:9e-8]#not before fit!!!
> plot  a * exp (-x*b) t titel("a",a,"b",b) lt 1,  c * exp (-x*d) t
> titel("a",c,"b",d) lt
> 2,  e * exp (-x*f) t titel("a",e,"b",f) lt 3,  g * exp (-x*h) t
> titel("a",g,"b",h) lt 4,
> '< sed "s/ 0/ ?0/g" dosis.dat' using 1:3 t "C_2: 1" ls 1 with lp, '< sed
> "s/ 0/  ?0/g"
> dosis.dat' using 1:4  t "C_2: 2" ls 2 with lp, '< sed "s/ 0/  ?0/g"
> dosis.dat' using 1:5
> t "C_2: 3" ls 3 with lp, '< sed "s/ 0/  ?0/g" dosis.dat' using 1:6 t "C_2:
> 4" ls 4 with lp
> 
> _______________________________________________________
> 
> 
> c_p= c_p + 1
> c_l= c_p + 2
> fit log(a)-b*x '< sed "s/ 0/  ?0/g" dosis.dat' using 1:(log(column(c_l)))
> via a, b
> #set yrange [1e-12:9e-8]#not before fit!!!
> plot '< sed "s/ 0/ ?0/g" dosis.dat' using 1:c_l t "C_2: $c_p" ls c_p with
> lp,  a * exp (-
> x*b) lt c_p
> if (c_p < 6) reread
> 
> ______________________________________________________
> 
> 
> set output "Dosis.png"
> set style line 1 lt 1 lw 2
> set style line 2 lt 2 lw 2
> set style line 3 lt 3 lw 2
> set style line 4 lt 4 lw 2
> #set terminal png font FreeSans 14 crop size 600,400
> set xrange [1:12]
> set xtics 1,1,11
> set label 1 'Spz' at graph 0.97, graph -.05
> set mytics 10
> set label 2 'I[A]' at graph -0.05, graph 0.99
> set key right top  Left reverse
> set termoption enhanced
> a= 5e-8
> b= .7
> FIT_LIMIT = 1e-9
> FIT_MAXITER = 0
> set log y
> c_p= 0
> set multiplot
> call 'dosis_single_fit.gpl' 'dosis.dat'
> unset multiplot
> 
>  
> 
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