Re: [Q] drawing straight lines in a Graph-like window

[Benedikt Stefansson]

Norberto Eiji Nawa wrote:
> 
> Hello:
> 
> I have a set of (x, y) coordinates that I would like to display in a
> window that looks like a Graph window (i.e. labels in the x-y axes,
> labels for the scale, auto-scale in the y axis).
> 
> The data is not a time series (demand and supply curves, actually), so
> I guess I will have to build everything using Canvas (and as a newbie,
> I am not exactly encouraged to do that). Does anyone have a better
> (easier) idea?
> 
> Thanks a lot in advance,
> 
> Eiji
> 
>                   ==================================
>    Swarm-Support is for discussion of the technical details of the day
>    to day usage of Swarm.  For list administration needs (esp.
>    [un]subscribing), please send a message to <address@hidden>
>    with "help" in the body of the message.

There is actually a FunctionGraph class which does pretty much exactly
what you want, however I think it can't handle two functions at the same
time:

http://www.santafe.edu/projects/swarm/swarmdocs/refbook/swarm.analysis.functiongraph.protocol.html

Here is another way to do the same, with an arbitrary number of
'functions'. You simply access Graph directly (EZGraph is a wrapper
around Graph and some other stuff. See also docs for Graph class).

Lets say you want to do a supply, demand curve graph. 
Start by creating the graph (e.g. WIDTH=400 HEIGHT=300)

  graph = [Graph createBegin: self];
  graph = [graph createEnd];
  [graph setTitle: "title"];
  [graph setWidth: WIDTH Height: HEIGHT];

Now create the graph elements, the curves:

  supply = [graph createElement];
  [supply setLabel: "supply curve"];  
  demand = [graph createElement];
  [demand setLabel: "demand curve"];

The rest I haven't actually tested, but this might be the way to draw
the
curves. For example 
 double x;
 double beta=1.0;
 double gamma=-1.0;

  for(x=0.0;x<1.0;x+=0.1) {     
   [supply addX: x Y: beta*x];
   [demand addX: x Y: gamma*x];  
  }

Finally display the graph:

  [graph pack];

To see this type of code in action, download the the ExperIPD example on
this webpage and
have a look at ObserverSwarm.m:
  http://www.sscnet.ucla.edu/99W/polisci209-1/

-Benedikt

---
Present coordinates: 
Dep. of Economics, Univ. of Trento, Via Inama 1, 38100 Trento, ITALY
Off: +39 0461 882246/267875 Mob: +39 347 0415721 Fax: +39 0461 882222

                  ==================================
   Swarm-Support is for discussion of the technical details of the day
   to day usage of Swarm.  For list administration needs (esp.
   [un]subscribing), please send a message to <address@hidden>
   with "help" in the body of the message.