How to reshape a vector without knowing the dimensions?

Hello,

I had a 3d matrix 663x3127x254. I removed NaN's using a mask and now I assume I have less elements on the left most dimension as in vector form:

s = 526593054 x 1, i = 67510073 x 1 (this is my mask, a magnitude lower)

How can I reshape the mask vector into a 3d matrix without knowing the new dimensions?

I am familiar with the function 'reshape' but only when I know the previous dimensions.

here is my code:

i = find(~isnan(s));
s = s(i);

My ultimate goal is to use it for triscatteredinterp.

thanks, Michael

Answer 1

[Christopher Berry]

Using reshape with only 2 dimensions specified will work only if the number of elements is such that the 3rd dimension fits exactly. You can do better by picking the 3 dimensions yourself using factor

factor(numel(s))

Multiply these factors any way you want to produce 3 non prime values. Then use these 3 non prime factor values with reshape. For example, if numel(s) = 64 :

factor(64)

ans = 
2 2 2 2 2 2

Then any of the following triples will work with reshape

(2,8,4) (4,4,4) (1,16,4)

Answer 2

[Azzi Abdelmalek]

You needat least, know the first two dimensions, the use

 reshape(i,663x3127,[])

but this is not always possible, depending of the size of i

Answer 3

[Sean de Wolski]

If you're using this for TriScatteredInterp, why do you need it as a three d array?

Couldn't you build it from a meshgrid (with corresponding nan points removed)?

% v is your matrix
[xx,yy,zz] = meshgrid(1:size(v,1),1:size(v,2),1:size(v,3));
idx = ~isnan(v);

xxv = xx(idx);
yyv = yy(idx);
zzv = zz(idx);
vv = v(idx);

T = TriScatteredInterp([xxv yyv zzv],vv)

I would also recommend using scatteredInterpolant over TriScattereredInterp if you're on a newer release.

Answer 4

[Michael]

Thanks guys! I managed to do it!