Re: Revised rlocus m-file

[Daniel J Sebald]

John W. Eaton wrote:
> On 13-Mar-2007, Daniel J Sebald wrote:
>
> | However, I'm getting back a
> | handle pointer which doesn't seem quite right.  In rlocus.m I placed
> | the following: 
> | 
> |     hplt = plot (args{:});
> |     get(hplt)
> | 
> | and I get 
> | 
> | ans = [...]
> | 
> | But this is the handle to the *zeros* only.  Should "plot", even
> | with this argument format, return a handle to the whole plot?  In
> | other words, if one goes to the __plt2vv__.m
> | 
> |     retval = line (x, y, "keylabel", key, "color", color,
> |                  "linestyle", options.linestyle,
> |                  "marker", options.marker);
> | 
> | which, I think, ends up being the retval, but that isn't the handle
> | for the whole plot, is it?
>
> If there are multiple lines created, the plot function should return a
> vector of handles for all the lines.  Try the following patch.
>
> | Also, I notice in the rlocus.m plot that the zeros are actually
> | filled dots, not open circles.  It turns out now that the
> | "pentagram" gets mapped to the open circle.  Currently in plot
> | options "o" in the filled circle.  Shouldn't "o" be the open circle,
> | not "pentagram"? 
>
> Yes.

Attached is a patch that rearranges symbols slightly.

o - open circle
. - filled circle (gnuplot's tiny little dot isn't a great plotting symbol)
"hexagram" - open square

and I've also touched up the rlocus.m file.  Let me know what you think.  (I'll 
send a PNG to John and ASH separately.)  Try it with

rlocus(zp([1+j, 1-j], [-1+2*j, -1-2*j,-5, -6, -7],1));



Dan

--- /usr/local/share/octave/2.9.9+/m/plot/__go_draw_axes__.m    2007-03-14 
19:34:42.000000000 -0600
+++ ./__go_draw_axes__.m        2007-03-14 22:21:26.422697312 -0600
@@ -812,11 +812,11 @@
       case "+"
        pt = "1";
       case "o"
-       pt = "7";
+       pt = "6";
       case "*"
        pt = "3";
       case "."
-       pt = "0";
+       pt = "7";
       case "x"
        pt = "2";
       case {"square", "s"}
@@ -834,7 +834,7 @@
       case {"pentagram", "p"}
        pt = "4";
       case {"hexagram", "h"}
-       pt = "6";
+       pt = "12";
       case "none"
        pt = "";
       otherwise
--- /usr/local/share/octave/2.9.9+/m/control/base/rlocus.m      2007-03-14 
19:34:28.000000000 -0600
+++ ./rlocus.m  2007-03-14 22:58:27.798996784 -0600
@@ -227,29 +227,63 @@
     if (! isempty (rlzer))
       nelts++;
     endif
+    # add asymptotes
+    n_A = length (olpol) - length (olzer);
+    if (n_A > 0)
+      nelts += n_A;
+    endif
     args = cell (3, nelts);
-    for kk=1:rows(rlpol)
-      args{1,kk} = real (rlpol (kk,:));
-      args{2,kk} = imag (rlpol (kk,:));
-      args{3,kk} = "b-";
+    kk = 0;
+    # asymptotes first
+    if (n_A > 0)
+      len_A = 2*max(abs(axlim));
+      sigma_A = (sum(olpol) - sum(olzer))/n_A;
+      for i_A=0:n_A-1
+        args{1,++kk} = [sigma_A sigma_A+len_A*cos(pi*(1+2*i_A/n_A))];
+        args{2,kk} = [0 len_A*sin(pi*(1+2*i_A/n_A))];
+        if (i_A == 1)
+          args{3,kk} = "k-;asymptotes;";
+        else
+          args{3,kk} = "k-";
+        endif
+      endfor
+    endif
+    # locus next
+    for ii=1:rows(rlpol)
+      args{1,++kk} = real (rlpol (ii,:));
+      args{2,kk} = imag (rlpol (ii,:));
+      if (ii == 1)
+        args{3,kk} = "b-;locus;";
+      else
+        args{3,kk} = "b-";
+      endif
     endfor
-    args{1,n_rlpol+1} = real(olpol);
-    args{2,n_rlpol+1} = imag(olpol);
-    args{3,n_rlpol+1} = "rx;open loop poles;";
-
+    # poles and zeros last
+    args{1,++kk} = real(olpol);
+    args{2,kk} = imag(olpol);
+    args{3,kk} = "rx;open loop poles;";
     if (! isempty(rlzer))
-      args{1,n_rlpol+2} = real(rlzer);
-      args{2,n_rlpol+2} = imag(rlzer);
-      args{3,n_rlpol+2} = "go;zeros;";
+      args{1,++kk} = real(rlzer);
+      args{2,kk} = imag(rlzer);
+      args{3,kk} = "go;zeros;";
     endif
 
-    plot (args{:})
+    set (gcf,"visible","off");
+    hplt = plot (args{:});
+    set (hplt(kk--), "markersize", 2);
+    if (! isempty(rlzer))
+      set(hplt(kk--), "markersize", 2);
+    endif
+    for ii=1:rows(rlpol)
+      set (hplt(kk--), "linewidth", 2);
+    endfor
     legend ("boxon", 2);
     grid ("on");
     axis (axlim);
     xlabel (sprintf ("Root locus from %s to %s, gain=[%f,%f]: Real axis",
                     inname{1}, outname{1}, gvec(1), gvec(ngain)));
     ylabel ("Imag. axis");
+    set (gcf,"visible","on");
     rldata = [];
   endif
 endfunction