How to use boxchart and GroupByColor when having a matrix?

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Amelie 2023-8-15

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评论： Amelie 2024-4-20

采纳的回答： Voss

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Dear all,

I am trying to use a boxchart for plotting a (10000,10) matrix, where each column represents a single box.

In other words, I would like to plot a boxchart consisting of 10 boxes and 10,000 data points.

The problem is that all Answers in the forum I have read so far are related to vectors, not matrices. All my attempts of using boxchart have resulted in an error, which states that I cannot use a matrix but vectors. Transforming the matrix into a vector is not possible. Additionally, I would like to group the 10 columns in 3 categories by assigning each box the respective color:

column [1 2 3 4 5 6 7 8 9 10]

group [A A B C C B A B C A]

color: [r r g b b g r g b r ]

However, I cannot provide a vector with values and tell Matlab to group the columns of the matrix on the basis of a specific threshold (e.g. temperature), but I have to do this manually by paper and pencil and inform Matlab which column belongs to which group myself.

I use the following code:

figure (2)
groupname={'A','A','B','C','C','B','A','B','C','A'}';
boxchart(AX.t_k,'MarkerStyle', 'none','GroupByColor', groupname); % AX.t_k = (10000,10) matrix

And I get the following error:

Error using boxchart

'GroupByColor' parameter is not supported when the sample data argument is a matrix.

Could someone tell me, how I can use boxchart when using a matrix and how I can group each column with their respective color?

Thank you very much for your help!

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采纳的回答

Voss 2023-8-15

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Maybe something like this:

% generate some random data:

N = 10000;

M = 10;

AX = struct('t_k',zeros(N,M));

for ii = 1:M

AX.t_k(:,ii) = rand()*rand(N,1)+rand();

end

% plot 10 separate boxcharts, and color each one appropriately:

groupname = {'A','A','B','C','C','B','A','B','C','A'};

colors = 'rgb';

colors = colors(findgroups(groupname));

[N,M] = size(AX.t_k);

hold on

for ii = 1:M

boxchart(AX.t_k(:,ii),'MarkerStyle','none','BoxFaceColor',colors(ii),'XData',ii*ones(N,1))

end

ax = gca();

ax.XAxis.Categories = categorical(1:M);

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Voss 2023-8-15

编辑：Voss 2023-8-15

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You're welcome!

ii*ones(N,1) is a 10000-by-1 column vector whose elements are all ii. As the loop iterates, ii goes from 1 to 10, so that's a column vector of 10000 1's the first time, then a column vector of 10000 2's the second time, and so on.

Including "'XData',ii*ones(N,1)" in the call to boxchart sets each respective boxchart's XData to the corresponding 10000-by-1 column vector. (XData has to be a vector the same size as the vector YData, which in this case is a column from your matrix, so that's why it's 10000-by-1.)

Setting the XData of each boxchart is necessary for the 10 different boxcharts to be located different x-locations (i.e., one boxchart at x = 1, one at x = 2, etc.). If you didn't specify that, they'd all be at x = 1 and overlapping.

Here's how it would look without specifying the XData:

% generate some random data:

N = 10000;

M = 10;

AX = struct('t_k',zeros(N,M));

for ii = 1:M

AX.t_k(:,ii) = rand()*rand(N,1)+rand();

end

% plot 10 separate boxcharts, and color each one appropriately:

groupname = {'A','A','B','C','C','B','A','B','C','A'};

colors = 'rgb';

colors = colors(findgroups(groupname));

[N,M] = size(AX.t_k);

hold on

for ii = 1:M

boxchart(AX.t_k(:,ii),'MarkerStyle','none','BoxFaceColor',colors(ii))%,'XData',ii*ones(N,1))

end

ax = gca();

ax.XAxis.Categories = categorical(1:M);

Voss 2024-4-19

在 MATLAB Online 中打开

Oh, I see. I thought you wanted them to be visible through the boxchart.

To make the boxcharts obscure the grid lines, you'd have to increase the BoxFaceAlpha property of the boxcharts, which controls their opacity. Default BoxFaceAlpha for a boxchart is 0.2; here I'll change it to 1 to completely obscure whatever is behind it:

% generate some random data:

N = 10000;

M = 10;

AX = struct('t_k',zeros(N,M));

for ii = 1:M

AX.t_k(:,ii) = rand()*rand(N,1)+rand();

end

% plot 10 separate boxcharts, and color each one appropriately:

groupname = {'A','A','B','C','C','B','A','B','C','A'};

% matrix of RGB triplets:

colors = [ ...

0 0.6 0; ...

0.6 0.6 0; ...

0.6 0 0.6; ...

];

% indexing by row:

colors = colors(findgroups(groupname),:);

figure

[N,M] = size(AX.t_k);

hold on

for ii = 1:M

% using one row of the colors matrix at a time:

boxchart(AX.t_k(:,ii), ...

'MarkerStyle','none', ...

'BoxFaceColor',colors(ii,:), ...

'XData',ii*ones(N,1), ...

'BoxFaceAlpha',1)

end

ax = gca();

ax.XAxis.Categories = categorical(1:M);

grid(ax,'on')

Unfortunately with that, as you can see, there's no longer a visual distinction between the box face and the box edge and median lines. To fix that, I'll make the BoxFaceColor lighter by changing the colors matrix, and keep the edge and median line colors as they were.

% matrix of RGB triplets:

colors = [ ...

0 1 0; ...

1 1 0; ...

1 0 1; ...

];

% indexing by row:

colors = colors(findgroups(groupname),:);

figure

[N,M] = size(AX.t_k);

hold on

for ii = 1:M

% using one row of the colors matrix at a time:

boxchart(AX.t_k(:,ii), ...

'MarkerStyle','none', ...

'BoxFaceColor',colors(ii,:), ...

'XData',ii*ones(N,1), ...

'BoxFaceAlpha',1, ...

'BoxEdgeColor',colors(ii,:)*0.6, ...

'BoxMedianLineColor',colors(ii,:)*0.6)

end

ax = gca();

ax.XAxis.Categories = categorical(1:M);

grid(ax,'on')

Voss 2024-4-20

You're welcome!

Hey, I'll take a fruit basket, sure. As long as the fruits are grouped by color.

Amelie 2024-4-20

Deal ! :)

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