gnuplot-info

[Gnuplot-info] read a single value from another datafile

[Peter B. <p....@vo...>]

Hi.

I'm not sure if there is a solution for this problem:
I want to read a single value from another datafile than the plotted 
file, and store the value in a variable for calculations while 
plotting.
The second datafile contains also columns of datas. So I have to 
specify the position of the value (field) where to read from.

e.g.
myvar = 'this_value_has_to_be_read_from_a_special_position_of_a_file'

plot 'datafile' using (($1-myvar)/86400):($3/$2*100)


Any ideas?
Thank you

Greetings from Germany

Peter

Re: [Gnuplot-info] read a single value from another datafile

[Hans-Bernhard B. <br...@ph...>]

Peter Bossy wrote:

> I'm not sure if there is a solution for this problem:
> I want to read a single value from another datafile than the plotted 
> file, and store the value in a variable for calculations while 
> plotting.

No way from inside gnuplot, I suspect (well, except maybe some seriously 
ugly hack involving a 'fit' of that data file...).  The usual way would 
be to assume piping capabilities, and let external tools do the job, i.e.:

	myvar = `program_to_extract_value_from -option filename`

Note that those are back-quotes ``, not ordinary '' ones.

Re: [Gnuplot-info] read a single value from another datafile

[Peter B. <p....@vo...>]

On Mittwoch, 19. Januar 2005 18:52, Hans-Bernhard Broeker wrote:
> Peter Bossy wrote:
> > I'm not sure if there is a solution for this problem:
> > I want to read a single value from another datafile than the
> > plotted file, and store the value in a variable for calculations
> > while plotting.
>
> No way from inside gnuplot, I suspect (well, except maybe some
> seriously ugly hack involving a 'fit' of that data file...).  The
> usual way would be to assume piping capabilities, and let external
> tools do the job, i.e.:
>
> 	myvar = `program_to_extract_value_from -option filename`
>
> Note that those are back-quotes ``, not ordinary '' ones.
>

Thanks, that works. Also with piping:

e.g.:

myvar = `head -n 1 filename | cut -f 4`

Have a nice weekend

Peter