why does this not work ?

for n=1:4 % size(PIDS,1); 
  BC = {n,4};
  BC{n,1} = {PIDS{n,1}; FNS{n,1}; PPNameS{n,1}; APS{n,1}};
  BC{n,2} = {PIDS{n,2}; FNS{n,2}; PPNameS{n,2}; APS{n,2}};
  BC{n,3} = {PIDS{n,3}; FNS{n,3}; PPNameS{n,3}; APS{n,3}};
  BC{n,4} = {PIDS{n,4}; FNS{n,4}; PPNameS{n,4}; APS{n,4}};
end
BC

[Jan]

We cannot know the reason, when you do not tell us what's going wrong. Do you get an error message or do the results differ from your expectations?

[Anne]

'Index exceeds matrix dimensions'

 then I tried to convert BC into an empty cell. 
then ive got another error 
Undefined variable "cell" or class "cell".

[Jan]

Please, Anne, post the complete error message. We do not have crystal balls and cannot guess the reason of the problems. Show us your code and care for a copy of the complete message. Obviously there is an error in your trial "to convert BC into an empty cell" - but I neitehr understand what "converting to an empty cell" means, nor how you've tried to implement this.

[Anne]

'Index exceeds matrix dimensions' is the complete error message.

[Jan]

No, a complete error message should contain the failing line also. Are you running tis in the command window? If so, create a script or even better a function. Then debugging is easier und you (and the readers) do not have to guess, where the error occurres.

I've edited my answer.

Answer 1

[Jan]

You overwrite BC in each iteration. Perhaps you want to move the pre-allocation before the loop:

BC = cell(4, 4);  % Not: {4, 4};
for n = 1:4 % size(PIDS,1); 
  BC{n,1} = {PIDS{n,1}; FNS{n,1}; PPNameS{n,1}; APS{n,1}};
  BC{n,2} = {PIDS{n,2}; FNS{n,2}; PPNameS{n,2}; APS{n,2}};
  BC{n,3} = {PIDS{n,3}; FNS{n,3}; PPNameS{n,3}; APS{n,3}};
  BC{n,4} = {PIDS{n,4}; FNS{n,4}; PPNameS{n,4}; APS{n,4}};
end

"BC = {n,4}" means, that BC is set to a [1 x 2] cell array. Is this intented? Afterwards the elements {n, 1:4} are added. But the values from the former itereations are overwritten.

To get the reason of the error message, write the code in a script or better a function. Then typ this in the command window:

dbstop if error

Now run your code again until it stops at the error. Inspect the variables and the indices: At least one of the arrays has less elements than you request.

[Image Analyst]

Anne, read this and this before you respond again. Also post some sample data for PIDS, FNS, PPNameS, and APS so we can try things to help you.