How can I give different colours not randomly to large number of lines in one plot?

The syntax in the code col=['r' 'y' 'b' 'g' 'k' 'c' 'm' 'k' '#D95319']; is related to the color of the lines in the plot which works well for 9 lines in the plot. But actually I want to plot 20 lines. How can I write this syntax for large number of colors? In fact, I don't want to give them random colors but in order.

clc
clear all

load EC.mat
for n=4:1:9;
    filename = sprintf('data_%d.mat',n);
    load(filename)
    E(n-3,:)=EC(1,:);
    d(n-3,:)=dep(9,:);
end
hold on ;  % MOVE THIS OUTSIDE THE LOOP
col=['r' 'y' 'b' 'g' 'k' 'c' 'm' 'k' '#D95319']; % MOVE THIS OUTSIDE THE LOOP
[m,~]=size(d);
lineHandles = gobjects(1,m); % ADD THIS
for i=1:m
    PP(i,:)=plot(d(i,:),E(i,:),'ok','LineWidth',2)% original data
    P1(i,:) = polyfit(d(i,:),E(i,:),2);%%2 indicates the quadratic
    % x_values =  min(in_(1,:)): 0.001:max(x_axis(1,:));
    Y= polyval(P1(i,:),d(i,:));
    h1 = plot(d(i,:),Y,'*g','LineWidth',1) % fitted
    Y1 = polyval(P1(i,:),d(i,:));
    R1 =  corrcoef(Y1,d(i,:));
    %%lsline
    ss = min(d(i,:)) : 0.001: max(d(i,:));
    Y2 = polyval(P1(i,:),ss);
    lineHandles(i) =  plot(ss,Y2,'color',col(i),'LineWidth',1);  % STORE HANDLE
end
% MOVE THIS OUTSIDE THE LOOP
title('Polynomial fitting','FontSize',16,'FontWeight','normal')
xlabel('Depolarisation ratio \delta_{in}','FontSize',12,'FontWeight','normal');
ylabel('Extinction coefficient \alpha{(m^-^1)}','FontSize',12,'FontWeight','normal');
ylim([0.005 0.03])
% SUPPLY HANDLES, DEFINE EACH POLY CURVE LINE
legend([PP(end,:), h1, lineHandles],...
    ["Actual data","Data fit",compose('PolyCurve %d\\mum',(4:m+7))],'location','Northwest')

[Walter Roberson]

col=['r' 'y' 'b' 'g' 'k' 'c' 'm' 'k' '#D95319']; % MOVE THIS OUTSIDE THE LOOP

needs to be either

col={'r' 'y' 'b' 'g' 'k' 'c' 'm' 'k' '#D95319'}; % MOVE THIS OUTSIDE THE LOOP

or

col=["r" "y" "b" "g" "k" "c" "m" "k" "#D95319"]; % MOVE THIS OUTSIDE THE LOOP

If you use the {} form then you need to use col{i} instead of col(i)

Answer 1

[Iuliu Ardelean]

Let's say you have 7 colours:

x = rand(7, 100);
y = rand(7, 100);
col = parula(7); % replace col=['r', 'y', 'b'] with col=parula(ColoursNumber)
figure
hold on
for i = 1:7
    plot(x(i,:),y(i,:), 'Color', col(i,:));
end
hold off
legend

If you don't like parula, you can try different ones from this list:

https://uk.mathworks.com/help/matlab/ref/colormap.html#buc3wsn-1-map

Image should look like this: