Re: How to use table header as title inside for loops?

[James R. V. Z. <jr...@co...>]

Ethan A Merritt wrote:
> On Sunday 15 March 2009, James R. Van Zandt wrote:
> > 
...
> >    
> > I would like to plot each datablock with its own title taken from the
> > third column.  I can use
> > 
> >   plot for [n=0:3] 'lab.dat' in n title 3
> > 
> > except that the first line of each datablock is not plotted. 
>
> Of course it isn't.  You have told the program that the first line
> contains labels, not data.

Right.  But I would like a way to tell the program that the first line
contains data that I would *also* like to use for labels.

> > Maybe what I want is
> > 
> >   plot for [n=0:3] 'lab.dat' in n title datastring(3)
> > 
> > but that isn't implemented?
>
> I don't know, because I don't quite understand what you are trying to do.
> How can every line of the data file contain a plot title?

I'm not necessarily plotting every datablock.  But the significant
thing about a datablock I do plot is that it has a constant value in
the third column.  So naturally I want to use that value for the
title.

> I could understand using each 3rd column value as a point symbol,
> or a color, or an xticlabel, etc,  but it doesn't make sense to have
> multiple titles for the same plot.

No, just one title.

> Maybe you are over-thinking this?  If that is really what your data file
> looks like, maybe you just want
>
>    plot for [n=0:3] 'lab.dat' in n title sprintf("Data block %d",n)

No, because it's the parameter value rather than the block number that
is significant.  In this particular case I could use

    plot for [n=0:3] 'lab.dat' in n title sprintf("parameter = %d",n+2)

but that would not work if the parameter values were not linearly
spaced, and would have to be manually adjusted every time the
parameter values changed.

> > BTW my application is a simulation where several of the columns have
> > input parameters, and the rest of the columns have outputs.  I can
> > plot one output as a function of two inputs using splot.  However, to
> > make it possible to actually read values off the curves, I would like
> > to plot iso-<whatever> lines: output as a function of one input
> > parameter, for selected values of a second parameter, and all other
> > parameters held constant.  It would be very helpful to get the curve
> > labels from the data file itself.
>
> Sorry, I still don't follow what you are aiming for.
> You are doing something to select  coordinate pairs from a subset of
> lines in the file.  OK.  But whatever set you pick within a single "plot"
> command can have only one title, right?

Let me try again.  Assuming this data file:

  # R     I      V  
  2000 0.001000  2
  2750 0.000727  2
  3500 0.000571  2
  4250 0.000471  2
  5000 0.000400  2
  
  
  2000 0.002500  5
  2750 0.001818  5
  3500 0.001429  5
  4250 0.001176  5
  5000 0.001000  5
  
  
  2000 0.005000 10
  2750 0.003636 10
  3500 0.002857 10
  4250 0.002353 10
  5000 0.002000 10

I'd like to plot current as a function of resistance, with the title
for each curve giving the voltage.

          - Jim Van Zandt