gnuplot-beta

array variables?

[<pl...@pi...>]

Hi,

I have to plot some data that depend on a parameter (pump speed) that I 
read in with each line of data. I need to calculate a plot value 
dependant on this value. I had it parametised as a function I call form 
the plot command but this is not accurate enough. I need it to be a 
look-up table (ie array) of values.

flo(dac)=flo_grad*(dac-16)+flo_0;

this needs to be

flo(dac)=speed[n];

I know use of variables is somewhat limited in gnuplot and I can't find 
any documentation that seems relevant. (array keyword referring to input 
format)

I have 16 values so a whole stack of 'if's would be pretty messy.

now am I missing a trick or is this simply not possible with the kind of 
algebra available within a gnuplot script?


best regards. Peter.

Re: array variables?

[Ethan A M. <sf...@us...>]

On Wednesday, April 06, 2011 06:05:23 am pl...@pi... wrote:
> Hi,
> 
> I have to plot some data that depend on a parameter (pump speed) that I 
> read in with each line of data. I need to calculate a plot value 
> dependant on this value. I had it parametised as a function I call form 
> the plot command but this is not accurate enough. I need it to be a 
> look-up table (ie array) of values.
> 
> flo(dac)=flo_grad*(dac-16)+flo_0;
> 
> this needs to be
> 
> flo(dac)=speed[n];
> 
> now am I missing a trick or is this simply not possible with the kind of 
> algebra available within a gnuplot script?

Not currently supported.
The closest we have is

  speed = " 1.11 2.22 3.33 4.44 5.55 "
  flo = word(speed,n)

Re: array variables?

[Bastian M. <bm...@ph...>]

Hello,

you might want to experiment with the following functions:

getArray(name, index) = value(sprintf("%s_%i", name, index))
setArray(name, index, value) = sprintf("%s_%i = %f", name, index, value)

Usage would be like this:

 > eval setArray("speed", n, val)
 > flo(n) = getArray("speed", n)

Maybe a function "evaluate()" to accompany the "eval" command would
be a worthwhile addition.

   Bastian

Am 06.04.2011 15:05, schrieb pl...@pi...:
> Hi,
>
> I have to plot some data that depend on a parameter (pump speed) that I
> read in with each line of data. I need to calculate a plot value
> dependant on this value. I had it parametised as a function I call form
> the plot command but this is not accurate enough. I need it to be a
> look-up table (ie array) of values.
>
> flo(dac)=flo_grad*(dac-16)+flo_0;
>
> this needs to be
>
> flo(dac)=speed[n];
>
> I know use of variables is somewhat limited in gnuplot and I can't find
> any documentation that seems relevant. (array keyword referring to input
> format)
>
> I have 16 values so a whole stack of 'if's would be pretty messy.
>
> now am I missing a trick or is this simply not possible with the kind of
> algebra available within a gnuplot script?
>
>
> best regards. Peter.