How can I plot multiple lines in different colors on a single plot using loops?

I am evaluating and plotting a function of time using at multiple times using a for loop and I want each line to plot a different color. My code plots all the lines the same color. At first my legend was not matching the lines so I am trying to plot the lines with defined colors and then change my legend accordingly. If anyone knows why the legends colors are out of order with the plot that would also help!

Cs is the function that varies with time.

Can someone suggest another way of doing this?

line_color = ['b' 'g' 'y' 'c' 'm' 'r'];

for i=1:length(t);
        figure(1)
        title('Carbon Sequestration in Indoor Environment vs. SA/V Ratio','FontSize',10)
        ylabel('Carbon Sequestration (kg CO2)')
        xlabel('SA/V Ratio')
        legend('25 years','50 years','75 years','100 years','125 years','150 years','AutoUpdate','off')
        hold on
        plot(SAV_ratio,Cs,line_color(i),'LineWidth',2)
end

Thanks

[jonas]

Is this only a small part of the loop? Because as it stands now, the loop seems rather meaningless. Second, you are plotting the entire set of data in every loop, with different colors. You probably have a lot more line handles than you desire. Finally, always save handles to the plot, especially when plotting in a loop.

h{i}=plot(SAV_ratio,Cs,line_color(i),'LineWidth',2)

[JoelB]

I know something isnt right but I am not sure how to approach this using a for loop. Maybe there is a better way to ensure the plot matches the legend. Here is the full code:

L=3; % measured in m
vtotal=0.75; % measured in m3
phi = 1.0; % assumed to be 1.0
alpha = 0.165;
beta = 0;
y = 0;
k0=3;
k1=1;
k2=1;
ppm=800;
n=0;
c=ppm/516e+3;
strength=40; % measured in MPa
m=(strength+7.4)/0.0825;
R=0.0016*strength^3.106;
line_color = ['b' 'g' 'y' 'c' 'm' 'r'];
t = [25 50 75 100 125 150]; % measured in years

for i = 1:length(t)
    x(i)=(2*c*t(i)/R)^0.5*(k0*k1*k2)^0.5*(1/t(i))^n;
end

SAV_ratio = [0:1:30]; % SA to Volume ratio
SA=SAV_ratio.*vtotal;

% this section calculates the sequestered carbon for each time, t, and for various
% surface areas. The if statement ensures the Vc does not exceed the volume of concrete.
for i = 1:length(t)
    for h = 1:length(SA)
        if x(i)*SA(h) >= vtotal
             Cs(i,h) = phi*(alpha-beta*y)*vtotal*m;
        else 
             Cs(i,h) = phi*(alpha-beta*y)*x(i)*SA(h)*m;
        end
    end
end

for i=1:length(t);
        figure(1)
        title('Carbon Sequestration in Indoor Environment vs. SA/V Ratio','FontSize',10)
        ylabel('Carbon Sequestration (kg CO2)')
        xlabel('SA/V Ratio')
        legend('25 years','50 years','75 years','100 years','125 years','150 years','AutoUpdate','off')
        hold on
        plot(SAV_ratio,Cs,line_color(i),'LineWidth',2)
end

[Image Analyst]

Joel, did you even see my answer below in the official "Answer" section of this page?

Answer 1

[Abby Skofield]

Starting in R2019b, use the colororder command to specify a palette of colors for individual plots to use. You can pass in color names like "b" and "blue" directly to the colororder command if those are the desired colors.

x = linspace(0,4*pi,100);
y = sin(x)+(1:6)';
plot(x,y,'LineWidth',2)

line_color = ["b" "g" "y" "c" "m" "r"];
colororder(line_color)

Starting in R2023b, there are several predefined, named palettes that can be used with the colororder command, for example'reef', 'meadow' and 'dye'.

clf
t = tiledlayout('horizontal');
ax1 = nexttile;
plot(ax1,x,y,LineWidth = 2)
colororder(ax1,'reef')
title('reef')
ax2 = nexttile;
plot(ax2,x,y,LineWidth = 2)
colororder(ax2,'meadow')
title('meadow')
ax3 = nexttile;
plot(ax3,x,y,LineWidth = 2)
colororder(ax3,'dye')
title('dye')

[Qian]

Works great! Thank you

[Qian]

For customized colors, [ ] does not work for me. I changed it to { }, it works well.

e.g.:

line_color = {'#66c2a5','#fc8d62','#8da0cb','#e78ac3','#a6d854'};

colororder(line_color)

[Adam Danz]

@Qian, you could also use

line_color = ["#66c2a5","#fc8d62","#8da0cb","#e78ac3","#a6d854"];

[Qian]

Thank you! It works with the doule quotation marks and [].

Answer 2

[Image Analyst]

Try this. Adapt as needed for your signal.

line_color = ['b' 'g' 'y' 'c' 'm' 'r'];

t = 1 : 100;
SAV_ratio = t;
ca = cell(1, length(line_color));
period = 100;
for k = 1 : length(line_color)
  ca{k} = sprintf('%d years', k*25);
  hold on
  % Get new values.
  Cs = sin(2*pi*t / (period * k));
  plot(SAV_ratio, Cs,'-', 'Color', line_color(k),'LineWidth',2)
  grid on;
end
title('Carbon Sequestration in Indoor Environment vs. SA/V Ratio','FontSize',16)
ylabel('Carbon Sequestration (kg CO2)')
xlabel('SA/V Ratio')
ax = gca;
ax.XAxisLocation = 'origin';
legend(ca, 'Location', 'southwest')

Answer 3

[Ivan Popov]

You have to use colororder(Colormap Name) with the desired color map. Then with one plot, you can use all desired colors in the appropriate order. Actually one can change colororder after data is plotted.

Example:

colororder(hsv(x));

plot(AnyMatrix(:,1:x));

[Adam Danz]

Doc to colororder (R2019B) : https://www.mathworks.com/help/matlab/ref/colororder.html