plotting of functions ...



hello,

i still have problems to plot functions ...

in an earlier post, i sent the code for the function, so here i onlz
post my problem:

nRTXI(T, TRATE) works if i call it like nRTXI(150, -30) ... put i can
not plot it, neither using plot2d nor plot3d ...

plot3d(nRTXI, [T, bfloat(T_Min), bfloat(T_Max)], [TRATE, bfloat(-50.0),
bfloat(-5.0)]);

Warning:  Float to bigfloat conversion of -50.0
Warning:  Float to bigfloat conversion of -5.0
Bad Range 
[T, 2.0B1, 1.7B2] must be of the form [variable,min,max]
 -- an error.  Quitting.  To debug this try DEBUGMODE(TRUE);


i do not understand maximas error-message, [T, 2.0B1, 1.7B2] is not of
the form [variable, min, max]?


thanks for hints,
robert