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

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

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