Precision & "densimetric" plots

[Sandro Dentella]

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Hi all,

1)
   I can't understand the behaviour of the following function as far as
   PRECISION is concerned:
   
   
   octave:1> function a=t(x)
   > a=x.^(1/3);
   > endfunction
   octave:2> a=85;
   octave:3> t(a)
   ans = 4.3968
   octave:4> a=[0,85];
   octave:5> t(a)
   ans =
   
     0.00000  4.39683
                    ^   Why shoud the precision be different?
   
   octave:6> a=[86,85];
   octave:7> t(a)
   ans =
   
     4.4140  4.3968
                   ^    Again like the first time. 

   Octave 1.1.1 - Linux 1.2.3            
2)    
   I would like to plot some functions in 2D, "densimetric fashion"
   (areas of a particular range of values rendered with the same shadow
   of gray or density of dots). The purpoise is to compare the result with
   photos of field-pattern from a laser. It would be enought to have it 
   done for post-script format: any suggestions?

   Thanks in advance for ideas and explanations  *:-)       
   
   
sandro dentella 
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