Plot2d Issue

Rich, Volker:

Thanks so much for your replies.  I've downloaded and installed the latest 
version of Maxima on my computer.  Unfortunately, I'm still getting the same 
error message.  The file I'm using is short, so I've included it here. 
Would you mind trying it and letting me know what you find?

Thanks,

Rich Wagner
Aerospace Engineer
Radical Novelties
Montrose, CO, USA


/* ==================================================================
   File: STEP AREA MESH SIZING.MAC

   This file finds an inverse-parabolic curve to fit the dA-dX
   data generated in our area step tests.

=====================================================================

   If we assume an equation of the form:

   dX = (a/dA^2) + (b/dA) + c

   We want this equation to pass through three points, (dA1,dX1),
   (dA2,dX2) and (dA3,dX3).  So,

   dX1 = (a/dA1^2) + (b/dA1) + c
   dX2 = (a/dA2^2) + (b/dA2) + c
   dX3 = (a/dA3^2) + (b/dA3) + c

   We can write this in matrix form as:

   [dX] = [dA][C]

   And we can solve for the coefficient matrix, [C] by,

   [dA]^-1 [dX] = [C]

================================================================== */

dA_1: 0.01;
dA_2: 0.02;
dA_3: 0.03;
dA_4: 0.05;
dA_5: 0.1;
dA_6: 0.2;

dX_1: 0.2;
dX_2: 0.1667;
dX_3: 0.1428;
dX_4: 0.0714;
dX_5: 0.02778;
dX_6: 0.01515;

P: matrix( [(1 / dA_1^2), (1 / dA_1), 1],
           [(1 / dA_4^2), (1 / dA_4), 1],
           [(1 / dA_6^2), (1 / dA_6), 1] );

S: matrix( [dX_1],
           [dX_4],
           [dX_6] );

C: invert(P) . S;


deltaX(a,b,c,dA):= (a / dA^2) + (b / dA) + c;


plot2d( [deltaX(C[1],C[2],C[3],Astep),
         [discrete,[
                    [dA_1,dX_1],[dA_2,dX_2],[dA_3,dX_3],
                    [dA_4,dX_4],[dA_5,dX_5],[dA_6,dX_6]
                   ]
         ]
        ],[Astep,dA_1,dA_6],
        [gnuplot_curve_styles,["with lines", "with points"]]
      );