Problem with applying a function (kstest) to cell arrays

Dear all,

I want to have the result of kstest (Kolmogorov-Smirnov test) for all arrays in a cell. In fact, I have a 1x93 cell that contains 93 doubles and the third column of these doubles is the column that I want to calculate kstest for. I searched and write this script:

for i=1:length(C1)
[h, p, k2stat] = arrayfun(@kstest, C1{1,i}(:, end), 'UniformOutput', false);
end

Although it runs successfully and the output is h with 336x1; I believe it gives me the wrong answer cause when I manually check some cell arrays it gives me the different answer (in some cases the output of my script reject null hypothesis while when I manually check it using this code:

kstest(C1{1,27}(:,end))

it's accepts the null hypothesis. So please let me what is my mistake if you know. I attached a small sample.

Thank you in advance

Answer 1

[Cris LaPierre]

The issue I see is you are using arrayfun, which applies the function to each element in the vector as opposed to each cell.

My recommendation is to use cellfun instead.

[h, p, k2stat] = cellfun(@(c)kstest(c(:,end)), C1);

On the other hand, you could also do this manually using a for loop.

for i=1:length(C1)
    [h(i), p, k2stat] = kstest(C1{i}(:, end));
end

Answer 2

[Image Analyst]

Is this what you're looking for?

s = load('C.mat')
C1 = s.C
numCells = length(C1)
for k = 1 : length(C1)
	thisArray = C1{k}; % Extract 2-D matrix.
	thisArray = thisArray(:, 3); % Extract only column 3.
	% Do kstest on column 3 only:
	k2stats(k) = kstest(thisArray);
% 	[h, p, k2stat] = arrayfun(@kstest, C1{1,i}(:, end), 'UniformOutput', false);
	% Visualize it
	subplot(4, 2, k);
	plot(thisArray, 'b.-');
	grid on;
	caption = sprintf('Array #%d', k);
	title(caption, 'FontSize', 18);
end
subplot(4, 2, 8);
bar(k2stats)
title('k2stats', 'FontSize', 18);
k2stats % Show in command window

See the link on Loren Shure's blog for a discussion:

Loren Shure's blog : Which Way to Compute: cellfun() or for-loop?