subplot and stem in matlab work but not work in octave of Discrete-time Signals

[eric]

| Dear octave expert:
| 
|    I copy some simple program from book "Digital Siganl Processing,
| using Matlab V.4" author by Vinay K.Ingle John G. Proakis from PWS
| published at page 15, example 2.2,
| 
|    my octave2.0.14 complain subplot and stem not be defined by gnuplot
| and stem.m file, so it also still can draw but not discrete graph
rather
| a connected(although not smooth, segmented) graph,
| 
|    Do any one know how to justify it, or where is the source code, we
| need to modify or adding new feature?
| 
| at matlab input
| >>n=-2:10; x=[1:7,6:-1:1];
| >>[x11,n11]=sigshift(x,n,5); [x12,n12]=sigshift(x,n,-4);
| >>[x1,n1]=sigadd(2*x11,n11,-3*x12,n12);
| >>subplot(2,1,1); stem(n1,x1); title('Sequence in Example 2.2a')
| >>xlabel('n'); ylabel('x1(n)');
|   
| 
| it should execute:
| x1(n) = 2x(n-5) -3x(n+4)
| 
| where x(n)= {1,2,3,4,5,7,6,5,4,3,2,1}
| 
| 
| Hope to get your(any octave expert) help (address@hidden)(Do octave
have
| any news group?)function [y,n] = sigadd(x1,n1,x2,n2)
| n=min(min(n1),min(n2)): max(max(n1), max(n2));
| y1=zeros(1,length(n)); y2=y1;
| y1(find((n>=min(n1))&(n<=max(n1))==1))=x1;
| y2(find((n>=min(n2))&(n<=max(n2))==1))=x2;
| y=y1+y2;
| 
| function [y,n] = sigshift(x,m,n0)
| n=m+n0;  y=x;
|



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