How to plot multi-line graph for nested loop?

Hi, I want to plot a multi-line graph for 2 ranges of variable input by user which are R and N. A graph of d_pred vs N must be plotted, whereby each line represents the d_pred calculated for each range of N at interval of 50 for each range of R input by users (interval 0.1). A table must be displayed for each of the lines plotted in the graph. The experimental value d_exp vs N must also be plotted in the same graph where it satisfies the range of N given and calculate AARD value between d_pred and d_exp representing each line plotted. Below is the code that I tried to run but failed. I used the nested loop command as the range of R and N affects each other in the equations used. Please help me.

% Given constants
p = 997;
Di = 0.01;
t = 40 * (10^-3);

% Prompt the user to input the range of variable N and R
N_range = input('Enter the range of variable N [start, end] (in rpm): ');
R_range = input('Enter the range of variable R [start, end]: ');

% Generate the range of variable N with intervals of 50
N_interval = 50;
N_values = N_range(1):N_interval:N_range(2);

% Initialize figure
figure;
% Nested loops to vary N and R
for i = 1:length(R_range)
    R = R_range(i);
    for j = 1:length(N_values)
        N = N_values(j)/60;
        
        % Calculate We for the current R value
        We = (p * (N^2) * (Di^3)) / t;
        
        % Calculate d_pred for the current R value
        d_pred = (0.0219 * (1 + 1.1309 * R) * (We^-0.6)) * Di;
        % Plot the graph for d_pred vs N for the current R
        plot(N, d_pred, 'LineWidth', 2, 'DisplayName', ['R=' num2str(R)]);
        hold on;
        
        % Display the values of N and d_pred at every interval in a table
        table_values = table(N', d_pred', 'VariableNames', {'N', 'd_pred'});
        disp(['Predicted Values (R=' num2str(R) '):']);
        disp(table_values);
        % Calculate and display AARD
        aard = mean(abs((d_exp - interp1(N_values, d_pred, N_exp))/d_exp));
        disp(['Absolute average relative deviation (AARD) between experimental droplet diameter and predicted droplet diamter is ' num2str(aard)]);
    end
    
end
% Experimental data
N_exp = [6000 7000 8000 9000];
d_exp_N = [11 9 8 7] * (10^-6);

% Display the values of N_exp and d_exp_N
table_values_exp = table(N_exp', d_exp_N', 'VariableNames', {'N_exp', 'd_exp'});
disp('Experimental Values (N):');
disp(table_values_exp);

% Add a plot for d_exp_N vs N in the same graph
scatter(N_exp, d_exp_N, 'r', 'filled', 'DisplayName', 'Experimental (N)');

% Add labels and legend
title('Nested Loop Graph: d\_pred vs N for Different R Values');
xlabel('N (rpm)');
ylabel('d\_pred');
legend('Location', 'Best');
grid on;
% Hold off to stop adding to the current plot
hold off;

Answer 1

[Sulaymon Eshkabilov]

From a quick scan the following inconsiostencies are spotted in your code.

(1) d_exp is not pre-defined but used in the loop. Maybe it d_exp_N then it should be define before the loop.

(2) R is not predicted value but pre-assigned from the user prompt of R_range.

(3) entries in interpolation .. interp1(N_values, d_pred, N_exp) is not correct. It should be .. interp1(d_pred, N_exp, N_values).

(4) size of d_pred and N_exp must match.

(5) why two value sof R_range is used. Probably it should be R_range_ii = linspace(R_range(1), R_range(2), N_interval).

(6) It looks like all calcs can be done using vectorization by matching the sizes of input entries.

[SHOMYA SRI]

Hi, can you elaborate more about the 1,2 and 5th points? I am sorry i couldn't understand that part as im still a beginner in Matlab.

[Sulaymon Eshkabilov]

(1) d_exp is not pre-defined but used in the loop. Maybe it d_exp_N then it should be define before the loop. See the calculation of variable aard:

...
    for j = 1:length(N_values)
    ...
    % Calculate and display AARD
        aard = mean(abs((d_exp - interp1(N_values, d_pred, N_exp))/d_exp));
        disp(...)
            

(2) R is not predicted value but pre-assigned from the user prompt of R_range. See your code:

      for i = 1:length(R_range)
        R = R_range(i);
        for j=length(N_values)
            ...
                % Display the values of N and d_pred at every interval in a table
        table_values = table(N', d_pred', 'VariableNames', {'N', 'd_pred'});
        disp(['Predicted Values (R=' num2str(R) '):']);
        

(5) why two values of R_range is used. Probably it should be R_range_ii = linspace(R_range(1), R_range(2), N_interval). R_range has two values only which are R_range(1) and R_range(2) correspond to [start, end]

R_range = input('Enter the range of variable R [start, end]: ');

[SHOMYA SRI]

Thank you, i'll look into it