I have a function that adds a legend I want to make the legend group certain plots together yet so that instead of a legend with 14 entries there is a legend with 5 entries

I have managed to make a code that automates the plotting of data but I would like the code to group the plots into disticnt groups.

Let us say samples 1,3,5 - is group 1

and 2,4,6- is group 2

7,9,11 group 3

8,10,12 is group 4

and finally 13 & 14 is group 5

this is the code

Nsamples = 7;
%
L = 100; % coupon gauge section (mm)
A = 17; % coupon cross-sectional area (mm^2)
%
figure(1);
hold;
figure(2);
hold
%
for k = 1:Nsamples
    %
    file_name = ['Sample' num2str(k) '.csv'];
    %
    T = readtable(file_name,'VariableNamingRule','preserve');
    %
    [test(k).disp,test(k).force,test(k).eyy] = post_fun(T);
    %
    figure(1)
    h(k) = plot(test(k).disp,test(k).force);
    set(h(k),'LineWidth',2);
    %
    figure(2)
    g(k) = plot(test(k).eyy*100,1000*test(k).force/A);
    set(g(k),'LineWidth',2);
    %
    leg_string{k} = ['Sample ' num2str(k)];
    %
end
%
figure(1)
set(gcf,'Position',[200 200 1024 768],'Color',[1 1 1]);
set(gca,'FontSize',24);
xlabel('Displacement (mm)','FontSize',32,'Interpreter','latex');
ylabel('Force (kN)','FontSize',32,'Interpreter','latex');
box on
grid on
legend(leg_string,'FontSize',28,'Interpreter','latex');
%
%
figure(2)
set(gcf,'Position',[200 200 1024 768],'Color',[1 1 1]);
set(gca,'FontSize',24);
xlabel('Strain (\%)','FontSize',32,'Interpreter','latex');
ylabel('Stress (MPa)','FontSize',32,'Interpreter','latex');
box on
grid on
legend(leg_string,'FontSize',28,'Interpreter','latex');
%
%
function [disp,force,eyy] = post_fun(T)
%
disp = table2array(T(:,4));
force = table2array(T(:,end));
eyy = table2array(T(:,10));
%
index = isnan(disp) | isnan(force) | isnan(eyy) | disp < 0 | force < 0 | eyy < 0;
%
disp(index) = [];
force(index) = [];
eyy(index) = [];
%
[~,index] = max(force);
disp(index+1:end) = [];
force(index+1:end) = [];
eyy(index+1:end) = [];
%
end

I have added sample 1-7 . csv but the code doesn't seem to run on this page.

this is what the figure1+2 looks like

Hopefully you can help.

Thanks

Alex

[Mathieu NOE]

hello

you could probably use this Fex submission to get to this result

GridLegend - File Exchange - MATLAB Central (mathworks.com)

so each group of 3 data could have same color and just different linestyle / markerstyle

other interesting legend tweaks are available on the same Fex (search "legend")

Answer 1

[dpb]

Nsamples = 7;
G=ones(1,2*Nsamples);
G(1:2:5)=1;
G(2:2:6)=2;
G(7:2:11)=3;
G(8:2:12)=4;
G(13:14)=5;
M={'x','+','*','s','d'};                        % a morker for each group
C={'r','b','k','m','g'};                        % and a color
L = 100; % coupon gauge section (mm)
A = 17; % coupon cross-sectional area (mm^2)
figure(1);
hold on
figure(2);
hold on
for k = 1:Nsamples
  file_name = ['Sample' num2str(k) '.csv'];
  T = readtable(file_name,'VariableNamingRule','preserve');
  [test(k).disp,test(k).force,test(k).eyy] = post_fun(T);
  ig=G(k);              % get group id for kth file
  figure(1)
  h(k) = plot(test(k).disp,test(k).force,'LineWidth',2,'Marker',M(ig),'Color',C{ig});

  figure(2)
  g(k) = plot(test(k).eyy*100,1000*test(k).force/A,'LineWidth',2,'Marker',M(ig),'Color',C{ig});
  leg_string{k} = ['Group ' num2str(ig)];
end
%
figure(1)
set(gcf,'Position',[200 200 1024 768],'Color',[1 1 1]);
set(gca,'FontSize',24);
xlabel('Displacement (mm)','FontSize',32,'Interpreter','latex');
ylabel('Force (kN)','FontSize',32,'Interpreter','latex');
box on
grid on
legend(h([1 2 7]),leg_string([1 2 7]),'FontSize',28,'Interpreter','latex','location','northwest');

figure(2)
set(gcf,'Position',[200 200 1024 768],'Color',[1 1 1]);
set(gca,'FontSize',24);
xlabel('Strain (\%)','FontSize',32,'Interpreter','latex');
ylabel('Stress (MPa)','FontSize',32,'Interpreter','latex');
box on
grid on
legend(g([1 2 7]),leg_string([1 2 7]),'FontSize',28,'Interpreter','latex','location','northwest');

function [displ,force,eyy] = post_fun(T)
  displ=T{:,4};
  force=T{:,end};
  eyy  =T{:,10};
  ix=all(isfinite([displ force eyy]),2) & all([displ force eyy]>0,2);
  displ=displ(ix);
  force=force(ix);
  eyy=eyy(ix);
  [~,imax] = max(force);
  displ(imax+1:end) = [];
  force(imax+1:end) = [];
  eyy(imax+1:end) = [];
end

The legends to display are those for the first element in each group so the linestyle, marker and color will match the legend string.

Answer 2

[Mathieu NOE]

this is a simple solution, where the files are processed in the order that you wished (cf list = [1 3 5 2 4 6 7 9 11 8 10 12 13 14]) , then visually afterwards we force the line color an style to follow a given order so the group is easily identified (appears also in the legend if that helps too)

here the result for figure 1 :

% Nsamples = 7;
%
L = 100; % coupon gauge section (mm)
A = 17; % coupon cross-sectional area (mm^2)
%
%
% pos array 
posA = [200 200 1024 768];
f1 = figure('Position',posA,'Color',[1 1 1]);    hold on
a1 = gca;
f2 = figure('Position',posA,'Color',[1 1 1]);    hold on    
a2 = gca;

% line style / colors 
colors = [
    0 0 1
    1 0 0
    0 0.75 0
    0.5 0 0.5
    1 0.5 0
    ];

styles = {'-','--','-.'};
inds = 0; % index for style indexing
spacing = size(styles,2); % period for style indexing
indc = 1; % index for color indexing

% Let us say samples 1,3,5 - is group 1
% and 2,4,6- is group 2
% 7,9,11 group 3
% 8,10,12 is group 4
% and finally 13 & 14 is group 5

% create a list of groups of 3 data files according to description above : 
% list = [1 3 5 2 4 6 7 9 11 8 10 12 13 14]
list = [1 3 5 2 4 6 7 ] % here we have only 7 files 

for ck = 1:numel(list)
    k = list(ck);
    % colors and linestyle index management
    inds = inds +1;
    if inds >spacing
        inds = inds - spacing;
        indc = indc +1;
    end
    %
    file_name = ['Sample' num2str(k) '.csv'];
    %
    T = readtable(file_name,'VariableNamingRule','preserve');
    %
    [disp,force,eyy] = post_fun(T);
    %

    h = plot(a1,disp,force,'LineWidth',2,"color",colors(indc,:),"linestyle",styles{inds});
    set(a1,'FontSize',24);
    xlabel(a1,'Displacement (mm)','FontSize',32,'Interpreter','latex');
    ylabel(a1,'Force (kN)','FontSize',32,'Interpreter','latex');
    box on;    grid on
    %

    g = plot(a2,eyy*100,1000*force/A,'LineWidth',2,"color",colors(indc,:),"linestyle",styles{inds});
    set(a2,'FontSize',24);
    xlabel(a2,'Strain (\%)','FontSize',32,'Interpreter','latex');
    ylabel(a2,'Stress (MPa)','FontSize',32,'Interpreter','latex');
    box on;    grid on

    %
    leg_string{ck,1} = ['Group ' num2str(indc) ' / Sample ' num2str(k)];
    %
end
%

legend(a1,leg_string,'FontSize',13,'Interpreter','latex');
legend(a2,leg_string,'FontSize',13,'Interpreter','latex');
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%ùù
function [disp,force,eyy] = post_fun(T)
%
% disp = table2array(T(:,4));
% force = table2array(T(:,end));
% eyy = table2array(T(:,10));

d = table2array(T); % one single call to table2array is enough
disp = d(:,4);
force = d(:,end);
eyy = d(:,10);
%
index = isnan(disp) | isnan(force) | isnan(eyy) | disp < 0 | force < 0 | eyy < 0;
%
disp(index) = [];
force(index) = [];
eyy(index) = [];
%
[~,index] = max(force);
disp(index+1:end) = [];
force(index+1:end) = [];
eyy(index+1:end) = [];
%
end

[A Poyser]

Thanks, I accepted the other answer just because it was the first that I read. But I have tried this one and it seems to work well too

[Mathieu NOE]

ok - no problem .

fyi, you can also vote for other answers that you find useful - that rewards people who spent time on your problem