edit_curv interactive graphic curve editor

## Syntax

    [x,y,ok,gc] = edit_curv(y)
                [x,y,ok,gc] = edit_curv(x,y)
                [x,y,ok,gc] = edit_curv(x,y,job)
                [x,y,ok,gc] = edit_curv(x,y,job,tit)
                [x,y,ok,gc] = edit_curv(x,y,job,tit,gc)

## Arguments

x

  vector of x coordinates

y

  vector of y coordinates

job

  a character string formed by one to three of the characters 'a','x','y'

  'a'

    to add points to the edited curve

  'x'

    to modify x coordinates of the edited curve points

  'y'

    to modify y coordinates of the edited curve points

tit

  a vector of three character strings which give the curve legend

gc

  a list of graphic window parameters: `gc=list(rect,nax)`

  rect

    bounds of the graphics (see plot2d for details)

  nax

    graduation parameters (see plot2d for details)

ok

  indicator if ok==%t user as returned with 'ok' menu else user as returned with 'abort' menu : list (graphical objects created under `edit_curv`

## Description

`edit_curv` is an interactive graphic curve editor. To add a new point simply click at the desired location, the added point will be connected to the nearest end-point. to move a point click on it, drag the mouse to the new position and click to set the new position