Re: Graphics Elements
- To: mathgroup at smc.vnet.net
- Subject: [mg8817] Re: [mg8779] Graphics Elements
- From: Allan Hayes <hay at haystack.demon.co.uk>
- Date: Fri, 26 Sep 1997 00:33:41 -0400
- Sender: owner-wri-mathgroup at wolfram.com
Edwin Wright <edwin.wright at ns.sympatico.ca>
[mg8779] Graphics Elements
> Does anyone know (Version 2.1.0) how to delete graphics elements
> from an existing graphic using AppendTo?
Edwin:
Consider the following (please enter the inputs to see the pictures)
In[1]:=
gr = Show[Graphics[{Circle[{0,0},1],Line[{{0,0},{1,1}}]}]]
Out[1]=
-Graphics-
The graphics expression
Graphics[{Circle[{0,0},1],Line[{{0,0},{1,1}}]}]
has been displayed by using the function Show. The picture is a
side effect. The output is hidden away in the special symbol
-Graphics-.
However, we can see it as follows
In[2]:=
InputForm[%]
Out[2]//InputForm=
Graphics[{Circle[{0, 0}, 1], Line[{{0, 0}, {1, 1}}]}]
(It is just the expression that we used Show on; we have called it gr)
Like any other Mathematica expression, we can manipulate it
In[3]:=
DeleteCases[gr,_Line, Infinity] (*remove any parts of the form
Line[...]*)
Out[3]=
-Graphics-
If we wish we cah see what has been done
In[4]:=
InputForm[%]
Out[4]//InputForm=
Graphics[{Circle[{0, 0}, 1]}]
We can show the picture that this defines
In[5]:=
Show[%]
Out[5]=
-Graphics-
We can alter the expression and show it with one line of code
In[6]:=
Show[gr/.Circle[p_,r_]:>{Hue[0],Circle[p-{1,0},r]}]
Out[6]=
-Graphics-
Allan Hayes
hay at haystack.demon.co.uk
http://www.haystack.demon.co.uk/training.html
voice:+44 (0)116 2714198
fax: +44 (0)116 2718642
Leicester, UK