Figures not showing up with for loop

Here is the for loop I'm using (I'm putting the whole thing for context), there should be 6 figures total, but I have only been able to get 2:

for i = 3:5 %for reynolds numbers 3e5 through 5e5
    for j = 1:16 %angles of attack -6 through 24
        temporary_data = data{i,j};
        for k = 1:44 %data columns
            deltaP = mean(temporary_data(k, 7:16)); % Delta P at specific airfoil sensor
            x = ((temporary_data(k, 1))/1000)/chord;
            temp = temporary_data(k,6)-32*(5/9)+273.15;
            q_transducer = temporary_data(k,5).*47.88;
            atmospheric = temporary_data(k,4).*6894.76;
            rho = atmospheric/(R.*temp);
            velocity = sqrt(2*q_transducer/rho); % Free-stream Velocity
            
            C_p = deltaP/(.5*rho*(velocity^2)); % Finding Coefficient of Pressure
            
            % Assign values to arrays
            %velocity_array(i, j, k) = velocity;
            CpArray = [CpArray; C_p];
            xArray = [xArray; x];
            
        end
        C_l = -1/chord * trapz(CpArray * cos(pi()/180 * alpha_range(j)));
        ClArray = [ClArray; C_l];
        
        n1 = i-2;
        figure(n1)
        grid on
        hold on
        plot(xArray, CpArray, 'm')
        set(gca, 'Ydir', 'reverse')
        xlabel('x/c')
        ylabel('C_p')
        titleVar = ['C_p vs. x/c for Reynolds Number: ', num2str(i), 'e5'];
        title(titleVar)
    end
    n2=n1+3;
    figure(n2)
    plot(-6:2:24, ClArray, '-*k')
    xlabel('alpha')
    ylabel('Cl')
    titleVar = ['Cl vs. alpha for Reynolds Number: ', num2str(i), 'e5'];
    title(titleVar)
end

Undefined variable 'data'.

[Dyuman Joshi]

We can't run your code to see the output it produces, as there is missing data and definitions. Please share all data that is required to run the code.

Also, you can use cosd instead of performing that conversion.

[Lauren]

Thank you

[Dyuman Joshi]

Any updates, @Lauren, Did @Voss's answer solve your problem?

Answer 1

[Voss]

Be sure to reset ClArray (and CpArray, xArray and whatever else should not carry over from one iteration of the outer (i) loop to the next) on each i loop iteration.

For example, doing that gives 6 figures:

data = repmat({rand(44,16)},5,16);
chord = 1;
R = 1;
alpha_range = rand(1,16);


for i = 3:5 %for reynolds numbers 3e5 through 5e5
    
    ClArray = [];
    CpArray = [];
    xArray = [];
    
   for j = 1:16 %angles of attack -6 through 24
       temporary_data = data{i,j};
       for k = 1:44 %data columns
           deltaP = mean(temporary_data(k, 7:16)); % Delta P at specific airfoil sensor
           x = ((temporary_data(k, 1))/1000)/chord;
           temp = temporary_data(k,6)-32*(5/9)+273.15;
           q_transducer = temporary_data(k,5).*47.88;
           atmospheric = temporary_data(k,4).*6894.76;
           rho = atmospheric/(R.*temp);
           velocity = sqrt(2*q_transducer/rho); % Free-stream Velocity
           
           C_p = deltaP/(.5*rho*(velocity^2)); % Finding Coefficient of Pressure
          
           % Assign values to arrays
           %velocity_array(i, j, k) = velocity;
           CpArray = [CpArray; C_p];
           xArray = [xArray; x];
         
       end
       C_l = -1/chord * trapz(CpArray * cos(pi()/180 * alpha_range(j)));
       ClArray = [ClArray; C_l];
     
       n1 = i-2;
       figure(n1)
       grid on
       hold on
       plot(xArray, CpArray, 'm')
       set(gca, 'Ydir', 'reverse')
       xlabel('x/c')
       ylabel('C_p')
       titleVar = ['C_p vs. x/c for Reynolds Number: ', num2str(i), 'e5'];
       title(titleVar)
   end
   n2=n1+3;
   figure(n2)
   plot(-6:2:24, ClArray, '-*k')
   xlabel('alpha')
   ylabel('Cl')
   titleVar = ['Cl vs. alpha for Reynolds Number: ', num2str(i), 'e5'];
   title(titleVar)
end

But initializing them before the loop produces an error when you try to plot ClArray against 16 x values because ClArray no longer has 16 elements the second time through the loop (i=4), and you end up with only 3 figures created.

CpArray = [];
xArray = [];
ClArray = [];
    
for i = 3:5 %for reynolds numbers 3e5 through 5e5
    for j = 1:16 %angles of attack -6 through 24
       temporary_data = data{i,j};
       for k = 1:44 %data columns
           deltaP = mean(temporary_data(k, 7:16)); % Delta P at specific airfoil sensor
           x = ((temporary_data(k, 1))/1000)/chord;
           temp = temporary_data(k,6)-32*(5/9)+273.15;
           q_transducer = temporary_data(k,5).*47.88;
           atmospheric = temporary_data(k,4).*6894.76;
           rho = atmospheric/(R.*temp);
           velocity = sqrt(2*q_transducer/rho); % Free-stream Velocity
           
           C_p = deltaP/(.5*rho*(velocity^2)); % Finding Coefficient of Pressure
          
           % Assign values to arrays
           %velocity_array(i, j, k) = velocity;
           CpArray = [CpArray; C_p];
           xArray = [xArray; x];
         
       end
       C_l = -1/chord * trapz(CpArray * cos(pi()/180 * alpha_range(j)));
       ClArray = [ClArray; C_l];
     
       n1 = i-2;
       figure(n1)
       grid on
       hold on
       plot(xArray, CpArray, 'm')
       set(gca, 'Ydir', 'reverse')
       xlabel('x/c')
       ylabel('C_p')
       titleVar = ['C_p vs. x/c for Reynolds Number: ', num2str(i), 'e5'];
       title(titleVar)
   end
   n2=n1+3;
   figure(n2)
   plot(-6:2:24, ClArray, '-*k')
   xlabel('alpha')
   ylabel('Cl')
   titleVar = ['Cl vs. alpha for Reynolds Number: ', num2str(i), 'e5'];
   title(titleVar)
end

Error using plot
Specify the coordinates as vectors or matrices of the same size, or as a vector and a matrix that share the same length in at least one dimension.

[Lauren]

I changed that and got 6 plots this time, thank you so much for your help! Your plots' titles changed with their corresponding Reynolds numbers, but when I run it, all of my plots use 5e5. Do you know why this could be? The data appears different in each both so I am assuming it's just the title that's off.

[Voss]

You're welcome! If this solved the problem, please "Accept this Answer". Thanks!

I'm not sure why the axes titles would be wrong. Are the axes xlabels and ylabels correct?

The only thing I could recommend is to check whether you have a variable or another function called "title", by running the command

which -all title

on the command line. That, and maybe try closing all figures before running your code and see if that works.