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How to select specific legend entries for bar chart

Asked by Hannah Sargeant on 27 Feb 2017
Latest activity Answered by Tiago Dias on 4 Jun 2019
I have written a code to produce a bar chart of results. The results have been calculated using 4 different methods and that is how I have coloured the bars. How do I create a legend with just the four colours I have chosen? Instead I can only get the first four entries in the chart, where three of them are the same colour:
% The code is as follows:
figure('name','Extraction energy analysis');
set(gca,'YScale','log')
hold on
for i=1:n
xlabel('Resource')
h=bar(i,output_Q_r(i));
if extraction(i) == 0
set(h,'FaceColor','g');
elseif extraction(i) == 1
set(h,'FaceColor','b');
elseif extraction(i) == 2
set(h,'FaceColor','y');
elseif extraction(i) == 3
set(h,'FaceColor','r');
end
end
hold off
set(gca,'xticklabel',resource)
ylabel('Energy (kW)')
X=(1:16);
XTickLabel=resource;
set(gca,'XTick',X) %assigning number of ticks to number of labels as automatically reaches limit of 15
title(char({'Energy required to extract 1000T of each resource',' from lunar south pole soil in 1 year'}))
xticklabel_rotate([],45)
legend('Thermal gas release',char({'hydrogen reduction',' of ilmenite'}),char({'electrolysis of',' molten regolith'}),'other')
end

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2 Answers

Answer by Rik
on 27 Feb 2017
 Accepted Answer

You can compile a vector of handles and use that as the pointer for legend
h_list=[];
hold on
for i=1:n
xlabel('Resource')
h=bar(i,output_Q_r(i));
if extraction(i) == 0
set(h,'FaceColor','g');
h_list(extraction(i)+1)=h;
elseif extraction(i) == 1
set(h,'FaceColor','b');
h_list(extraction(i)+1)=h;
elseif extraction(i) == 2
set(h,'FaceColor','y');
h_list(extraction(i)+1)=h;
elseif extraction(i) == 3
set(h,'FaceColor','r');
h_list(extraction(i)+1)=h;
end
end
hold off
set(gca,'xticklabel',resource)
ylabel('Energy (kW)')
X=(1:16);
XTickLabel=resource;
set(gca,'XTick',X) %assigning number of ticks to number of labels as automatically reaches limit of 15
title(char({'Energy required to extract 1000T of each resource',' from lunar south pole soil in 1 year'}))
xticklabel_rotate([],45)
legend(h_list,'Thermal gas release',char({'hydrogen reduction',' of ilmenite'}),char({'electrolysis of',' molten regolith'}),'other')
end

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That's great! Thank you very much

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Answer by Tiago Dias on 4 Jun 2019

Hi, what is extraction?

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