How do I save multiple PCA results in a cell array? Error: Brace indexing not supported

Hi,

I have this raw data set which includes 18 participants. Each participants raw data (21 columns) is saved in a cell. I would like to run a principal component analysis on each cell and then collect each type of output in a new cell array.

So basically I run:

for i = 1:length(file_list);
    [coeff{i},score{i},latent{i},tsquared{i},explained{i},mu{i}] = pca(cell2mat(pre_data{i,1})); % convert each cell to a matrix and run the PCA on each cell
end

I would like to save all coeff outputs for each participant in a cell array, each score output for each participant in a cell array, and so on...

This way I would have six new cell arrays with 18 cells each in which I have the PCA outputs for each participant.

But somehow the code above gives me the error:

"Unable to perform assignment because brace indexing is not supported for variables of this type."

How would I solve this?

Thnaks!

Answer 1

[Star Strider]

I am not certain what the problem is.

This runs without error for me, and produces the appropriate result —

LD = load('pre_data.mat');
pre_data = LD.pre_data;

for i = 1:length(pre_data);
    [coeff{i},score{i},latent{i},tsquared{i},explained{i},mu{i}] = pca(cell2mat(pre_data{i,1})); % convert each cell to a matrix and run the PCA on each cell
end

The only difference is that this iterates on the length of ‘pre_data’ not ‘file_list’ since I only have the cell arrays.

.

[lil brain]

Hi @Star Strider thanks for the feedback! When I run your code I seem to get the same error unfortunately. Very strange ...

[Star Strider]

I still don’t know what is throwing the error, however I suspect it has to do with the addressing of the outputs rather than the argument.

Try preallocating them as cell arrays —

Lc = numel(pre_data);

coeff = cell(Lc,1);

score = cell(Lc,1);

... and so for the rest.

[lil brain]

Hi @Star Strider I noticed that the issue was gone after I cleared all the variables and ran it again. So its all good now. Thanks for your help!

[Star Strider]

My pleasure.