with gnuplot 4.3 it's possible:
normalize to the maximum yvalue:
max(a,b)=a>b?a:b
a=99999999.
plot 'datafile' using 1:(a=max(a,$2),0/0) notitle, '' using 1:($2/a) with
linespoints
explanation:
1st you plot nothing ('0/0') but you determine the maximum value in
column '2', in the 2nd plot you use this maximum value.
instead of determining the maximum yvalue you could also choose any
yvalue (e.g. the one in line '4' of your datafile):
plot 'datafile' using 1:(a=$2,0/0) every 1:1:3:0:3:0 notitle, '' using
1:($2/a) with linespoints
uli80 wrote:
>
> Dear all,
>
> I've been using Gnuplot since years as my standard plotting tool. But
> there is one thing, that I still could not find out. Maybe there is anyone
> in this forum who can answer the following question:
>
> I have a data file containing two columns: x and y values.
> How can I get access to one value a = y(x)?
>
> This value I need e.g. to normalize all values in a plot:
>
> plot 'data.txt' using 1:($2/a)
>
>
> Thank you very much for any idea!!
>

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