Creating a legend inside a loop, using sprintf

I am trying to make a legend for a plot with 'beta' number of curves. Basically, beta would be beta = [1 : 5] if I decided to have five curves, but it can be any number. I want to make a legend for that number of curves, and specifically do this by using a for loop (I know there are other ways that don't need for loops but I want to use a for loop for this one specifically). The code that I have (below) just gives me a legend for one curve "beta=1beta=2beta=3beta=4beta=5". I would need a legend for five curves. Basically the first curve would be beta = 1, the second curve would be beta = 2, and so on. Can someone help me?

for beta_val = beta
    plot(time, y);
    hold on
    lgd = sprintf('beta = %0.0f', beta);
    legend(lgd);
    end

Answer 1

[Star Strider]

Try something like this:

time = linspace(0, 2*pi);                                           % Create Data
beta = 1:5;                                                         % Create Data
y = sin(time(:)*beta);                                              % Create Data

for beta_val = beta
    plot(time, y(:,beta_val));
    hold on
    lgd{beta_val} = sprintf('beta = %0.0f', beta(beta_val));
end
legend(lgd);

[positron96]

So if I use your code, and append it to mine:

clear; clc; 

alpha = 0.1; % degradation rate
time = [0 : 0.5 : 10]; % a vector for time ranging from 0 1o 10 seconds, in intervals of 0.5 second
beta = transpose([1 : 5]); % a vector for the production rate ranging from 1 to 5, in intervals of 1

y = zeros(5, 21); % initializing a matrix of zeros to store all mRNA expression levels (y) for each beta value (and each point in time); 5 beta values, 20 points in time

for time_point = 1 : length(time)
    for beta_val = beta 
        y(beta_val, time_point) = beta ./ alpha .* (1 - exp(-alpha .* time(time_point)));

      end

end

for beta_val = beta
    plot(time, y(:,beta_val));
    hold on
    lgd{beta_val} = sprintf('beta = %0.0f', beta(beta_val));
end
legend(lgd);

I get the following error:

Error using plot Vectors must be the same length.

Error in testcode (line 23) plot(time, y(:,beta_val));

[positron96]

Oh I figured it out! Thank you so much!

[Star Strider]

You have row vectors for ‘y’. My code has column vectors. So with that and one other tweak, and using MATLAB’s vector and matrix vectorisation abilities to eliminate the first loop, we have:

alpha = 0.1; % degradation rate
time = [0 : 0.5 : 10]; % a vector for time ranging from 0 1o 10 seconds, in intervals of 0.5 second
beta = transpose([1 : 5]); % a vector for the production rate ranging from 1 to 5, in intervals of 1

y = beta ./ alpha .* (1 - exp(-alpha .* time));

for beta_val = 1:numel(beta)
    plot(time, y(beta_val,:));
    hold on
    lgd{beta_val} = sprintf('beta = %0.0f', beta(beta_val));
end
legend(lgd, 'Location','N')

See if that does what you want.

[positron96]

This actually works a ton better! Thanks so much!

[Star Strider]

As always, my pleasure!

[Jan]

If this works, you can omit the loop:

plot(time, y);
lgd{beta_val} = sprintfc('beta = %0.0f', beta);
legend(lgd, 'Location','N')

Answer 2

[Kai Åsvik]

I am getting this error message: "Function 'subsindex' is not defined for values of class 'cell'."

[Jan]

@Kai: The problem is solved already and the readers cannot guess, which code causes your problem. Please open a new thread and include the code and the complete error message.