[R] 3D-plotting a 2D-matrix that contains z-values (3rd dimension)

[Uwe Ligges]

On 09.06.2011 13:37, oliver wrote:
> On Thu, Jun 09, 2011 at 11:22:54AM +0200, Uwe Ligges wrote:
>> Well,
>>
>> persp(x, y, z) does exactly what you asked for: it plots tha matrix
>> z along the values given by the vectors x and y.
>
> But I don't have these vectors x and y, so I have to
> create them just to call persp().
> And persp also needs the values only to rise.
>
> But if I have x and y, and I want to have only rising numbers for x and y,m
> I need somehow to create those values, and expand.grid()
> would not create value combinations that are only rising.
> (Or did I miss an option for expand.grid, which does that?)
>
>> If you need to calculate z values from x and y using some function
>> foo, outer(x, y, foo) is typically your friend.
>
> OK.
>
> And what, if I want to generate the mathcing x- and y- values
> for a matrix, that has x- and y implicitly, but I only have the
> z-values inside the matrix?
>
> So, my problem is the other way around.
> I don't want to calc the z for my x-and y, I want to generate the x-
> and y- values for my matrix of z-values.


Actually you just need to pass the matrix Z if the scale of the axes is 
irrelevant:

persp(Z)

Uwe Ligges


>
> Ciao,
>     Oliver