Interpolate a 4D matrix to increase its size

Hi!

i have a 4D matrix B its size is 40*64*40 and i want to increase it to be 250*400*250 ,i know that if we multiplie the first size with 6.25 we will get the final size that we want, i know i should use the interp3 for that ,i tried it i did [X,Y,Z]=size(B);

V=6.25*size(B1);

[Xq,Yq,Zq]=[250 400 250];

B1=interp3(X,Y,Z,V,Xq,Yq,Zq);

But it dosen't work . please can any one help me with that ? specialy that i am not used to work with 4D matrix ,I used to use imresize() for 2D matrix!!

thank you so muchh

[Jan]

A "4D" matrix should have 4 dimensions, not 3. I assume, you mean a "3D array".

"It doesn't work" is a lean description of what happens. Please mention, what you observe and what you want instead.

[rachida]

i have a 4D matrix with X Y Z and T but i want just to change the first 3 dimensions and keep the fourth one.

[Stephen23]

"i have a 4D matrix B its size is 40*64*40"

That is a 3D array (unless you are bothering to arbitrarily count one implicit trailing singleton dimension). Why do you keep insisting that an array with three consecutive non-singleton dimensions is a "4D matrix" ?

[rachida]

in fact i have an image 4D 40*64*40*8 ( it s an IMR image 8 means the number of canals tha we have ) , i just didnt explain the situation in a good way.at the end i changed the dimension

Answer 1

[Jan]

[X,Y,Z] = size(B);
B1      = interp3(1:X, 1:Y, 1:Z, B, ...
                  linspace(1, X, 250), ...
                  linspace(1, Y, 400), ...
                  linspace(1, Z, 250));

[rachida]

HI Jan thank you for your help but i got an error as (Error using permute

ORDER must have at least N elements for N-D array

error in iterp3 v=permute(v,p);

is that could be because my matrix is 4D dimension but i am intrested in the first 3 dimension the fourth one i dont want to change it

[rachida]

HI thank you i found my error in fact i should not neglige the fourth dimension

[Jan]

Yes, if B has 4 dimensions, you have to consider this explicitly. Simply use interpn:

[X,Y,Z,T] = size(B);
B1        = interp3(1:X, 1:Y, 1:Z, 1:T, B, ...
                  linspace(1, X, 250), ...
                  linspace(1, Y, 400), ...
                  linspace(1, Z, 250),
                  1:T);  % Last dimension untouched

Answer 2

[Matt J]

B1=imresize3(B,[250,400,250]);

[rachida]

Hi

thank you for your answer i already tried this function but matlab dosent reconize it , it gives me undefined function or variable and he suggested imresize()

[rachida]

HI thank you i found my error in fact i should not neglige the fourth dimension

[Jan]

There is an imresize3 since R2017b: https://www.mathworks.com/help/images/ref/imresize3.html

The documentation of imresize claims, that "any dimension" is handled, but some tests show, that this concerns 2D gray-scale images and [X * Y * N] arrays only, while for the later only the 1st 2 dimensions are scaled and the last one is treated as color channels.

Answer 3

[Matt J]

If your data truly does have 4 dimensions, then you can use imresizen

https://www.mathworks.com/matlabcentral/fileexchange/64516-imresizen-resize-an-n-dimensional-array

B1=imresizen(B,[6.5,6.5,6.5,1]);