[Gnuplot-bugs] feature request

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

Hi,

I have been trying to trick gnuplot into doing some simple tasks it does=
  =

not seem possible to do but which could be immensely useful.

to judge by comp.graphics.apps.gnuplot it seems that there are certain  =

basic tasks that are frequently requested and get a reply along the line=
s  =

of "gnuplot is not for number crunching".

Fine. Gnuplot is a plotting program, not a data processing package but  =

there are an number of trivial tasks like calculating a mean or finding =
 =

the max of values *calculated* by gnuplot that cant currently be done.

Tasks like this are far less complex than function fitting do data or  =

plotting with spline interpolation and would be very valuable in the  =

context of outputting data to a graph.

eg how to put a label at the max point of the data. Definately a plottin=
g  =

task and hardly "number crunching" but currently it seems I have do this=
  =

simple task in an external script.

Worse, if I do some fitting and expression evaluation in the plot comman=
d  =

, I have to duplicate it all to a table, call an external script and the=
n  =

read in a new file to get the value of the max or mean value of y.

all I really need is a means to assign one tiny little variable during  =

plot (directly or from a within a fn )

consider the following that will plot a "sample and hold":

xmax=3D0;
max(x)=3D( (xmax<x)?(xmax=3Dx):xmax  );

plot  "150tank-txC.data"   using 1:(Th6($4)) with lines t "panel out" \
, "150tank-txC.data"   using 1:(max(Th6($4))) with lines t "s/h" ;


Currently not possible since function parser will not allow C style  =

'assignment returns a value'.
A similar technique could find the min , max, mean or area under graph; =
in  =

fact it opens a whole range of possibilities that are frequently request=
ed  =

on the list.


So how much effort is it?

Well without going to the extent of supporting procedure calls from with=
  =

plot command , adding the above parsing of C style assignments would be =
 =

simple to add and open the door to some very useful techniques.

I hope you will find it worth considering.

Kind regards.