gnuplot-info

[Gnuplot-info] for loop iterating functions

[stibala <ada...@gm...>]

Hello, 
I have a matrix data set, each column contains a curve and I have a function
fitted to each curve.
I need to plot the original curves minus the respective fitted function and
here comes the problem.
My wanted code with for loop is
 p for [i=2:11] "data.txt"  u 1:(column(i) - function>i<($1))
so I can't imagine how to iterate through my functions numbered as the
corresponding columns in data.
It can be done without the loop simply
p "data.txt" u 1:($2 - function2($1)), "data.txt" u 1:($3 - function3($1)),
...
but I would like to plot it within the loop because I have a lot of data.
All the functions are the same, but with different constants, for example
g2(x)=exp(a2*x+b2)+c2 and g3(x)=exp(a3*x+b3)+c3.

Thank you for your help

Adam Stíbal



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Re: [Gnuplot-info] for loop iterating functions

[Theo <th...@gm...>]

Hi Adam,

would this help to solve your problem?

a1 = 0.1	# define all your constants
a2 = 0.2
a3 = 0.3
b1 = 1.2
b2 = 2.3
b3 = 3.4
c1 = -1
c2 = -2
c3 = -3
# define a(n),b(n),c(n)-functions
a(n) = a1*(n==1) + a2*(n==2) + a3*(n==3) # and so on...
b(n) = b1*(n==1) + b2*(n==2) + b3*(n==3)
c(n) = c1*(n==1) + c2*(n==2) + c3*(n==3)
# define your function which will be subtracted
GPFUN_g = "g(n,x) = exp(a(n)*x+b(n))+c(n)"

I haven't tested it to the very end but if you using the function g(n,x) 
and something like the following...

plot for [2:11] "data.txt" using 1:(column(i) - g(i,$1))

There might be certainly a more elegant way to do it...
Anyway, let me know whether it works or not.

Theo.

Re: [Gnuplot-info] for loop iterating functions

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

stibala <adam.stibal <at> gmail.com> writes:

> 
> Hello, 
> I have a matrix data set, each column contains a curve and I have a function
> fitted to each curve.
> I need to plot the original curves minus the respective fitted function and
> here comes the problem.
> My wanted code with for loop is
>  p for [i=2:11] "data.txt"  u 1:(column(i) - function>i<($1))
> so I can't imagine how to iterate through my functions numbered as the
> corresponding columns in data.
> It can be done without the loop simply
> p "data.txt" u 1:($2 - function2($1)), "data.txt" u 1:($3 - function3($1)),
> ...
> but I would like to plot it within the loop because I have a lot of data.
> All the functions are the same, but with different constants, for example
> g2(x)=exp(a2*x+b2)+c2 and g3(x)=exp(a3*x+b3)+c3.
> 
> Thank you for your help
> 
> Adam Stíbal
> 
> --

pass the loop variable as a second argument to the
function and distinguish between the different loop
steps using the ternary operator:
(here: from 2 to 5)

g(x,column)=\
 column==2?exp(a2*x+b2)+c2:\
  column==3?exp(a3*x+b3)+c3:\
   column==4?exp(a4*x+b4)+c4:\
    column==5?exp(a5*x+b5)+c5:\
     0/0

Re: [Gnuplot-info] for loop iterating functions

[stibala <ada...@gm...>]

Thank you gentlemen, this was definitely helpful.
The definition of a special function to distinguish between all the
functions is the trick.
The code for plot is then pretty elegant.

Thank you again

Adam



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