How to reshape a vector without knowing the dimensions?

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)

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Answer 2

Azzi Abdelmalek 2014-8-5

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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

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Answer 3

Sean de Wolski 2014-8-5

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编辑：Sean de Wolski 2014-8-5

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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)