How can I fix this problem

 U=[];
 for a=1:numel(TI(1).Si)      % Universe
     % U = [U TI(1).Si{a}];
 end
 U = unique(U,'first');

Cell contents reference from a non-cell array object.

[Nicolas B.]

Can you provide the part where you define and/or modify TI before that loop?

[Mira le]

TI is a structure : TI = repmat (ch, N,1)

ch is aleary declared like ch.Si={}

I want to copy value of Si in U and the remove duplicate value in U

[Walter Roberson]

T(1).Si is an array but not a cell array, somehow. Something you did in storing data to it made it not a cell.

[Mira le]

How can I fix it then