How to simplify legend when grouping by 2 variables, with unique colors for one and unique shapes for the other

This question is a follow-up to my previously-answered question: https://www.mathworks.com/matlabcentral/answers/797552-how-to-group-by-2-variables-with-unique-colors-for-one-and-unique-shapes-for-the-other?s_tid=prof_contriblnk

The offered solution provides a legend with every combination of the two variables being grouped by. How do I simplify it, so that Input is shown once for each associated color (maybe all points for the shape), and each Year shape is shown once, in black?

Here is the code from the solution:

% Original data
Year = [2016    2016    2017    2017    2018    2018    2016    2016    2017    2017    2018    2018    2016    2016    2017    2017    2018    2018];
Input = [0   0   0   0   0   0   1   1   1   1   1   1   2   2   2   2   2   2];
Response = [4704.5  4059.5  10891   11440.5 4083.5  2876    11459.66667 11752   11566   12036   11323.5 11118.5 10296.5 10234   13074.5 14166   9062    9669];
% Reormat the data
Year = min(reshape(Year,2,[]),[],1)';
Input = min(reshape(Input,2,[]),[],1)';
Response = reshape(Response,2,[])';
% Visualize the data
Data = array2table([Year,Input,Response],'VariableNames',["Year","Input","T1","T2"])

figure
mrkr = {'.','s','^'};
ax = axes;
hold on
Yr = unique(Data.Year);
for y = 1:length(Yr)
    ind = Data.Year == Yr(y);
    % just plot data for this year, specifying marker style and turning legend off
    gscatter(ax,Data.T1(ind),Data.T2(ind),Data.Input(ind),[],mrkr{y},[],'off');
    ax.ColorOrderIndex = 1;
end
hold off
% Use some string manipulation to create legend labels for all color+marker combinations
legend(Yr' + "_" + unique(Data.Input),'NumColumns',length(Yr),'Interpreter',"none",'Location',"best")

Answer 1

[Vatsal]

Hi,

I understand you want to simplify the legend so that each "Input" is associated with a unique color, and each "Year" shape is represented once in black.

Below is the modified code for that purpose:

Year = [2016    2016    2017    2017    2018    2018    2016    2016    2017    2017    2018    2018    2016    2016    2017    2017    2018    2018];
Input = [0   0   0   0   0   0   1   1   1   1   1   1   2   2   2   2   2   2];
Response = [4704.5  4059.5  10891   11440.5 4083.5  2876    11459.66667 11752   11566   12036   11323.5 11118.5 10296.5 10234   13074.5 14166   9062    9669];
Year = min(reshape(Year,2,[]),[],1)';
Input = min(reshape(Input,2,[]),[],1)';
Response = reshape(Response,2,[])';
Data = array2table([Year,Input,Response],'VariableNames',["Year","Input","T1","T2"])

figure
mrkr = {'.','s','^'};
ax = axes;
hold on
Yr = unique(Data.Year);
h = []; % Initialize an empty array to hold your plot handles
for y = 1:length(Yr)
    ind = Data.Year == Yr(y);
    % Store the plot handles when plotting
    h = [h; gscatter(ax,Data.T1(ind),Data.T2(ind),Data.Input(ind),[],mrkr{y},[],'off')];
    ax.ColorOrderIndex = 1;
end
hold off

% Create a legend for the colors (Inputs)
legend(h(1:3), 'Input 0', 'Input 1', 'Input 2', 'Location', 'northwest')

% Create a second axes for the second legend
ax2 = axes('Position',ax.Position,'Visible','off');

% Create a legend for the shapes (Years)
line('Parent',ax2,'XData',nan,'YData',nan,'Marker',mrkr{1},'Color','k','DisplayName','Year 2016', 'MarkerFaceColor', 'k', 'LineStyle', 'none');
line('Parent',ax2,'XData',nan,'YData',nan,'Marker',mrkr{2},'Color','k','DisplayName','Year 2017', 'MarkerFaceColor', 'k', 'LineStyle', 'none');
line('Parent',ax2,'XData',nan,'YData',nan,'Marker',mrkr{3},'Color','k','DisplayName','Year 2018', 'MarkerFaceColor', 'k', 'LineStyle', 'none');
legend(ax2,'Location','southeast') % Change this to 'southeast' for bottom right

I hope this helps!