interp and interp3 give different size arrays

If I start with the following two arrays

 x0 = 1:100;
 y0 = 1:80;
 z0 = 1:100;

and I make a mesh grid with them

 [X0, Y0, Z0] = meshgrid(x0, y0, z0);

Now if I plug in x0 into interp and use a factor of 2 I get

 xw = interp(x0,2);

 size(xw)

 ans = 
      1   200

Doing the same but with interp3 I expect to get a 160 x 200 x 200 array instead I get

 Xw = interp3(X0,2);

 size(Xw)

 ans =

      317   397   397

which is just 3 less than an additional factor of 2.

Why is that and how can I correct that?

I have some flow data that is in an N x M x P array A

 M = length(x0);
 N = length(y0);
 P = length(z0);

 size(A)

 ans = 

      80   100   100

using these numbers. I want to interpolate the 3D data onto a finer mesh rN x rM x rP where r is some integer >= 2. Can I do this with interp3 or do I need to use something else?

Answer 1

[ANKUR KUMAR]

x0 = 1:100;
y0 = 1:90;
z0 = 1:100;
data1=randi(10,90,100,100); %defining data over coarser resolution

dimension of data1 should be dim(y0)x dim(x0)x dim(z0). See the comment to this answer for more clarification

[x0_mesh,y0_mesh,z0_mesh]=meshgrid(x0,y0,z0);

%finer points
Xr =1:0.5:90; %defining the finer resolution points.
Yr =1:0.5:100;
Zr= 1:0.5:100;
[Xr_mesh,Yr_mesh,Zr_mesh]=meshgrid(Xr,Yr,Zr);
data1_finer_grid=interp3(x0_mesh,y0_mesh,z0_mesh,data1,Xr_mesh,Yr_mesh,Zr_mesh);
size(data1)
size(data1_finer_grid)

[ANKUR KUMAR]

x0 = 1:10;
y0 = 1:20;
z0 = 1:30;
data1=rand(20,10,30); 
size(data1)

ans =

      20    10    30

data1 should be 20x10x30. if your data is in 10x20x30, then firstly permute the matrix and switch the dimension.

data2=rand(10,20,30)
data2=permute(data2,[2,1,3])
size(data2)

ans =

      20    10    30

[Nathaniel H Werner]

Yes I realized I was able to do so after making a finer meshgrid first as well