Skip entries in a legend when plotting from a table

I have got a table from which I'd like to plot two fields ('Analysis' against 'Date'). The 'Analysis' field is a table itself, and I am plotting a particular field from it (PMkW_corr_298_RPMcorr). The health_monitor_log table has a field, 'Unit', from which I'd like to include unique values of in the legend. Each unique Unit has a different marker and/or colour.

I have tried the code below, but it doesn't seem to exclude repeat values of Unit from the legend. So for my first unique Unit entry, I'm expecting a triangle marker in the legend, and for the second unique Unit, a diamond. But when I type two entries for the legend in, I get two triangles, which is because the first two entries in the table have the triangle markers.

                          [c,ia,ic]=unique(health_monitor_log.Unit);
                          marker={'^','d','<','>','s','p','h'};
                          colour={'k','r','y','g','b','c','m'};
                          for i=1:size(health_monitor_log,1)
                              hold on
                              if any(strcmp('etath_PM_kW',fieldnames(health_monitor_log.Analysis{i,1})))                           
                                  p=plot(health_monitor_log.Date(i),health_monitor_log.Analysis{i}.PMkW_corr_298_RPMcorr,'Marker',char(marker(health_monitor_log.Marker(i))),'MarkerFaceColor',char(colour(health_monitor_log.Colour(i))),'MarkerEdgeColor',[1,1,1])
                                  if ~ismember(i,ia)
                                      ant=get(p,'Annotation');
                                      if iscell(ant)
                                          for j=1:length(ant)
                                              set(get(ant{j},'LegendInformation'),'IconDisplayStyle','off')
                                          end
                                      else
                                          set(get(ant,'LegendInformation'),'IconDisplayStyle','off')
                                      end
                                  end
                              end
                          end

[Peter Perkins]

This

   health_monitor_log.Analysis{i}.PMkW_corr_298_RPMcorr

suggests that Analysis is not a table, but rather a cell array of tables. Nothing at all wrong with that, it would be a collection of data sets, each one tagged by a date, I guess? But then you are plotting it against Date(i) which seems like it would be ONE date.

It would help to see a simple example of what data you have.

[Afzal Ali]

Please see comments on answer below for example data

Answer 1

[Afzal Ali]

Solution was to restructure the table into a cell array ('plot_cell'), and use a handle array with 'DisplayName' property assigned to each handle as shown in How to show partial legend in figure

                        marker={'^','d','<','>','s','p','h'};
                        colour={'k','r','y','g','b','c','m'};

                        plot_cell=cell(size(health_monitor_log,1),1);

                        for i=1:size(health_monitor_log,1)
                            if any(strcmp('etath_PM_kW',fieldnames(health_monitor_log.Analysis{i,1})))
                                ss=health_monitor_log.Analysis{i};
                                ss.Date(:,1)=health_monitor_log.Date(i);
                                ss.Unit(:,1)=health_monitor_log.Unit(i);
                                ss.Marker(:,1)=health_monitor_log.Marker(i);
                                ss.Colour(:,1)=health_monitor_log.Colour(i);
                                plot_cell{i}=ss;
                            end
                        end

                        plot_cell=plot_cell(~cellfun('isempty',plot_cell));

                        h = zeros(size(plot_cell,1),1);
                        unit_names_list=repmat("String",size(plot_cell,1),1);
                        unique_unit_count=0;
                        for i=1:size(plot_cell,1)
                            unit_name=plot_cell{i}.Unit(1);
                            h(i)=plot(plot_cell{i}.Date,plot_cell{i}.PMkW_corr_298_RPMcorr,'Marker',...
                                 char(marker(plot_cell{i}.Marker(1))),'MarkerFaceColor',...
                                 char(colour(plot_cell{i}.Colour(1))),'MarkerEdgeColor',...
                                 [1,1,1],'LineStyle','none','DisplayName',...
                                 char(plot_cell{i}.Unit(1)));
                            hold on
                            if ~ismember(unit_name,unit_names_list)
                                unique_unit_count=unique_unit_count+1;
                                legend_idx(unique_unit_count)=i;
                            end
                            unit_names_list(i)=plot_cell{i}.Unit(1);
                        end
                        legend(h(legend_idx))

Answer 2

[Rik]

Use explicit handles in your call to legend. Make sure you only pass 1 element of each type into the handle array.

h_d=plot(1,2,'d');
hold on
h_t=plot([.5 .7;.6 .8],[1.5 1.5;1 1],'*');
legend([h_d(1) h_t(1)],{'diamond','triangle'})

[Afzal Ali]

This would require me to have a handle for each unique value. The problem is I wouldn't know how many unique values there are.

[Rik]

That p in your code is a handle to a line object. You can use that to populate an array of handles. What is the problem precisely? I don't have your data, so I can't really reproduce what you want. Can you provide some dummy data that looks like the data you have?

[Afzal Ali]

Here's the structure of the table I am looking at. The legends should only appear for unique values in the Unit field.