Code covered by the BSD License

# Group means with letters in a multiple comparison test

### Cleiton Nunes (view profile)

Grouping means by letters in a multiple comparison test

phgroup(xo,c)
```function phg = phgroup(xo,c)
%
% Input:
% x: data matrix with treatments in rows and observations in columns
% c: matrix of pairwise comparison results from multcompare test
%
% WARNING: is indispensable that the means of x matrix are sorted in crescent order.
%
% Example:
%
% For 3 treatments in 4 replications:
%	x=[9.0 1.0 3.1
%      5.0 2.0 3.2
%      7.0 1.1 3.0
%      8.0 1.2 3.0];
%
% Sorting x in crescent order:
%	[me or]=sort(mean(x),2);
%	xo=x(:,or);
%
% ANOVA:
%	[p,a,s] = anova1(xo);
%
% Multcompare using HSD Tukey at 5% significance:
%	[c,m,h,nms] = multcompare(s,'alpha',0.05,'ctype','hsd');
%
% Post-hoc grouping:
%	phg = phgroup(xo,c);
%
% By Cleiton A. Nunes
% UFLA,MG,Brazil

% Getting significant pairwise comparisons
gr=1;
for i=1:size(c,1)
if c(i,3)>0&&c(i,5)>0||c(i,3)<0&&c(i,5)<0
tt(c(i,2),c(i,1))=0;
gr=gr+1;
else
tt(c(i,1),c(i,1))=gr;
tt(c(i,2),c(i,1))=gr;
end
end

% Setting groups if all non-significant
if isempty(find(tt>0))==1
for i=1:size(tt,1)
gr=gr+1;
tt(i,i)=gr;
end
end

% Setting groups if some non-significant
for i=1:size(tt,1)
if isempty(find(tt(i,:)>0))==1
tt(i,i)=gr+1;
gr=gr+1;
end
end

% Correcting repeated groups
for i=1:size(tt,2)-1
if max(find(tt(:,i+1)>0))==max(find(tt(:,i)>0))
tt(find(tt(:,i+1)>0),i+1)=tt(i,i);
end
end
mx=max(tt);
for i=1:size(tt,2)-1
if max(tt(:,i+1))==mx(i)
tt(find(tt(:,i+1)>0),i+1)=0;
end
end

% Setting sequential groups
[B,IX] = sort(nonzeros(max(tt))');
for l=1:size(tt,1)
for c=1:size(tt,2)
if tt(l,c)>0
for u=1:size(B,2)
if tt(l,c)==B(u)
tt(l,c)=IX(u);
end
end
end
end
end

% Assigning letters to groups
gn=['a';'b';'c';'d';'e';'f';'g';'h';'i';'j';'k';'l';'m';'n';'o';'p';'q';'r';'t';'u';'v';'w';'x';'y';'z'];
for i=1:size(tt,1)
tg=[];
ttu=nonzeros(unique(tt(i,:)))';
for j=1:size(ttu,2)
tg=[tg gn(ttu(1,j))];
TG{i,1}=tg;
end
end

% Getting output table
m1=[mean(xo);std(xo)]';
m1=[num2cell(m1) TG];
me1=['mean';m1(:,1)];
st=['std';m1(:,2)];
gr=['group';m1(:,3)];
phg=[me1 st gr];```