Question: How do I solve invalid input in the proc?

April 07 2012 docoi 5

0

Hey,

i have 2 differential equations and want to solve the first one when x is positive and the second when x ist negativ. For this problem i wrote the follwing procedure. But when i try i have the posted error. Has someone a good idea to help me?

Thanks a lot

 

> DGL3 := 10*(D(D(x)))(t) = x(t);

> DGL4 := 10*(D(D(x)))(t)+5000 = x(t);

 

Tsolver:=proc()
global DG1, DG2, func, var, var_min, var_max, x, Dx, N:
global dt, F1, DF1, ti, i:
    DG1:=args[1]:
    DG2:=args[2]:
    func:=args[3]:
    var:=op(1, args[4]):
    var_min:=op(1, op(2, args[4])):
    var_max:=op(2, op(2, args[4])):
    x[0]:=args[5]:
    Dx[0]:=args[6]:
    N:=args[7]:
    dt:=(var_max-var_min)/N:
    i:=0:
    
 for ti from var_min by dt to var_max
    do i:=i+1:
         if x[i-1]>0
        then
                 F1:=dsolve({DG1, func = x[i-1], diff(func, var) = Dx[i-1]}, numeric):
            x[i]:=F1(ti):
            DF1:=diff(F1, var):
            Dx[x-i]:=DF1(ti):
    
        else
    
                F1:=dsolve({DG2, func = x[i-1], diff(func, var) = Dx[i-1]}, numeric):
            x[i]:=F1(ti):
            DF1:=diff(F1, var):
            Dx[x-i]:=DF1(ti):
         fi:
   od:
end;

 

And this is the problem when i try to use this procedure:

 

> debug(Tsolver);
print(`output redirected...`); # input placeholder
                                   Tsolver
> A := Tsolver(DGL3, DGL4, x(t), t = 0 .. 4, .2, .196, 60);
%;
{--> enter Tsolver, args = 10*((D@@2)(x))(t) = (table( [( 0 ) = .2 ] ))(t), 10*((D@@2)(x))(t)+5000 = (table( [( 0 ) = .2 ] ))(t), (table( [( 0 ) = .2 ] ))(t), t = 0 .. 4, .2, .196, 60
                          10 @@(D, 2)(x)(t) = ()(t)
                      10 @@(D, 2)(x)(t) + 5000 = ()(t)
                                    ()(t)
                                      t
                                      0
                                      4
                                     0.2
                                 20.00000000
                                      0
                                      1
<-- ERROR in Tsolver (now at top level) = invalid input: %1 expects its %-2 argument, %3, to be of type %4, but received %5}
Error, (in unknown) invalid input: `dsolve/numeric/lexorder` expects its 2nd argument, b, to be of type {indexed, name, numeric}, but received table( [( 0 ) = .2 ] )

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