# How to use multiple grouping variables in boxplot? Why box plot grouping variable 'not same length' error?

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Daniel Bridges 2018년 2월 27일
댓글: Issa 2019년 8월 28일
1. How do I use multiple grouping variables?
2. How do I resolve the borrowing incorrect error?
Error message:
>> BoxplotGICategoriesDVH
Error using boxplot>straightenX (line 969)
G must be the same length as X or the same length as the
number of columns in X.
Error in boxplot (line 273)
[xDat,gDat,origRow,xlen,gexplicit,origInd,origNumXCols]
= straightenX(x,g);
Error in BoxplotGICategoriesDVH (line 8)
boxplot(data,group)
Verifying that G is "the same length as the number of columns in X":
>> length(group)
ans =
3
>> data
data =
4 18 30
5 8 9
Code causing the error:
data = round(10*rand(2,3));
data(:,2)=2*data(:,2);
data(:,3)=3*data(:,3);
group = cell(3,1);
group{1} = {'1','a'};
group{2} = {'2','b'};
group{3} = {'3','c'};
boxplot(data,group)
How do I resolve this error?
##### 댓글 수: 1표시숨기기 없음
Daniel Bridges 2018년 2월 27일
편집: Daniel Bridges 2018년 2월 27일
For a simple example, I'm currently trying to boxplot to compare data A and B from year 1 and 2; the first two columns being data A, columns 2 and 4 being year 2:
data = round(10*rand(10,4));
data(:,2)=2*data(:,2);
data(:,4)=4*data(:,4);
The end goal is to group by three toxicity categories over 60 dose intervals. I'm trying here just to learn the syntax, what code MATLAB wants to see to get the correct boxplot.

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### 채택된 답변

Daniel Bridges 2018년 2월 28일
편집: Daniel Bridges 2018년 2월 28일
This StackOverflow answer appears to contain the solution I'm seeking.
This code works:
data = round(10*rand(10,4));
data(:,2)=2*data(:,2);
data(:,3)=3*data(:,3);
data(:,4)=2*3*data(:,4);
group = {reshape(repmat('A':'B',2,1),4,1) repmat((1:2)',2,1)};
boxplot(data,group)
Apparently the error was caused by having a cell array with cells being 1x4 vectors instead of 4x1 vectors.
Removing the repmat and reshape commands for simplicity:
data = round(10*rand(10,4));
data(:,2)=2*data(:,2);
data(:,3)=3*data(:,3);
data(:,4)=2*3*data(:,4);
group{1} = {'1';'1';'2';'2'};
group{2} = {'a';'b';'a';'b'};
The problem was caused by using commas instead of semi-colons, i.e. a row vector instead of a column vector.

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### 추가 답변(1개)

Jan 2018년 2월 27일
I'm not sure what you are exactly asking for. But maybe this helps:
data = round(10*rand(2,3));
data(:,2) = 2*data(:,2);
data(:,3) = 3*data(:,3);
group = {'a', 'b', 'c'}
boxplot(data, group)
##### 댓글 수: 2표시숨기기 이전 댓글 수: 1
Issa 2019년 8월 28일
how to set different Whisker for each group in matlab boxplot

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