Kruskal Wallace Test on Column

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Sarah Yun
Sarah Yun on 15 Dec 2019
Edited: Adam Danz on 17 Dec 2019
Hi,
I have three seperate tables.
There is one column in each table I want to compare - temperature
The data are not normally distributed.
So, I can use a Kruskal Wallace test to compare the means of the three columns
My problem: the test seems to work on 1 array only (x) - but I have three
How should I write the code to conduct the test?
I tried concatenating the tables but they each have a different number of rows - so it is not working.
Advice welcome.

Answers (1)

Adam Danz
Adam Danz on 15 Dec 2019
Edited: Adam Danz on 15 Dec 2019
The p = kruskalwallis(x) test works on columns of x. If all of your tables have the same number of rows, you just have to extract the values from each table into a matrix. If the tables only have 1 variable, as you described, it's as easy as,
T1 = table(rand(20,1));
T2 = table(rand(20,1)+1);
T3 = table(rand(20,1)+.5);
p = kruskalwallis([T1{:,:},T2{:,:},T3{:,:}])
% or
p = kruskalwallis([T1.Var1,T2.Var1,T3.Var1])
If the tables do not have equal rows, you must concatenate them into a single column and use a grouping variable p = kruskalwallis(x,group)
x = [T1.Va1;T2.Var1;T3.Var1];
group = [1 + zeros(size(T1.Var1)); 2 + zeros(size(T2.Var1)); 3 + zeros(size(T3.Var1))];
p = kruskalwallis(x,group)
  2 Comments
Sarah Yun
Sarah Yun on 15 Dec 2019
Hi Adam,
Unfortunately, my 3 tables do not have equal rows. So, I must use a grouping variable. Please can you help me with this? Thank you. Sarah.
Adam Danz
Adam Danz on 15 Dec 2019
Edited: Adam Danz on 17 Dec 2019
Yep! I just added an example at the bottom of my answer. If you get stuck, show me the code you're using and describe the problem and I'd be happy to help straighten things out.

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