given a scalar field function f(x,y,z), how to plot it in maple?

I can't find a suitable command, if I missed, please tell me.

thank you for any advice.

1. how to eliminate the diff(*(x,y,z),x) terms in an expression, "*" means any function which have independent variables x,y,z?

2. how to get the gradient of a vector, which should be a tensor?

restart;
pp:=-55471918776960000*tanh((1/3220)*sqrt(10368400-cp^2)*Pi*x/cp)+5350094400*tanh((1/3220)*sqrt(10368400-cp^2)*Pi*x/cp)*cp^2-129*tanh((1/3220)*sqrt(10368400-cp^2)*Pi*x/cp)*cp^4+2670899840*tanh((1/6450)*sqrt(41602500-cp^2)*Pi*x/cp)*sqrt(41602500-cp^2)*sqrt(10368400-cp^2);
Student[Calculus1]:-Roots(subs(x=8000,pp),cp=1..3220,numeric);
p1:=proc(v)
option hfloat;
local a;
a:=Student[Calculus1]:-Roots(subs(x=v,pp),cp=1..3220,numeric);
if nops(a)>=1 then seq([v,a[i]],i=1..nops(a));
end if;
end proc:
SS1:=[seq(p1(i),i=3500..20000,200)]:
plot(SS1,style=point,gridlines);

The final figure is different between maple12 and maple17.

On 17, unwanted points apprear.

is it a bug?

restart;
a=1-(1+x)*exp(-x);
SS:=solve(%,x,allsolutions);
evalf(eval(SS,[_Z2=0,a=0.3]));evalf(eval(SS,[_Z2=-1,a=0.3]));

I know there are two branches for the lambertw function meet my demand.

I wonder whether there is a method to find the _Z2 value with SS::real, for the above commands, they are 0&-1.

thank you for any advice.

restart;
with(ArrayTools):
M1 := Matrix([[0, 0, b], [0, e, f]], order = Fortran_order);
row, col, var := SearchArray(M1);
M2 := Matrix([[0, 0, b], [0, e, f]], order = C_order);
row2, col2, var2 := SearchArray(M2);

I guess that's a bug.