# Question:Points in cylindrical plot

## Question:Points in cylindrical plot

Hello people in mapleprimes,

I am writing this question, hoping you to teach me about the meanig of the Array in a plot3d object.

```c:=plot3d(x*y,x=0..2,y=0..1,coords=cylindrical,grid=[3,2]);
lprint(c);
```

makes

`PLOT3D(MESH(Array(1 .. 3, 1 .. 2, 1 .. 3, {(1, 2, 3) = HFloat(2.), (2, 2, 1) = HFloat(1.08060461173627953), (2, 2, 2) = HFloat(1.68294196961579301), (2, 2, 3) = HFloat(2.), (3, 2, 1) = HFloat(-1.66458734618856963), (3, 2, 2) = HFloat(3.63718970730272684), (3, 2, 3) = HFloat(2.)}, datatype = float[8])))`

I thought I had known the cylindrical coords.
And, I think that (1, 2, 3) in  (1, 2, 3) = HFloat(2.) means the value of x*y when x, the angle, =0, y, the hight, =1, z, distance from the origin, =3. And, it should become 0, as the value of x, times 1, the value of y, equals 0. But, it takes HFloat(2.) as
shown in (1, 2, 3) = HFloat(2.).

And, as for (3, 2, 1) = HFloat(-1.66458734618856963), which means x=2 and y=1, I think the value of x*y=2. But,
it is wrong as seen in  (3, 2, 1) = HFloat(-1.66458734618856963).

I hope you will teach me how to consider about sample points in the cylindrical plot.