# How to output a for to a 10x27 table (for loop keeps overwriting the variable)

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Marshall Thompson el 3 de Dic. de 2023
Comentada: Marshall Thompson el 6 de Dic. de 2023
I am trying to iterate an equation using a range of values as a linspace(2, 3, 10) for one variable and set of 27 variable for the second variable.
The equation I am trying to iterate is assigned to a variable sigma_x_case1 (See Attached - Equation.png)
The For Loop that I currently have is as follows:
height_range_data = linspace(2, 3, 10);
diameter_range_data = [0.405, 0.54, 0.675, 0.84, 1.05, 1.315, 1.66, 1.9 ,2.375, 2.8753, 5, 4, 4.5, 5, 5.563, 6.625, 8.625, 10.75, 12.75, 14, 16, 18, 20, 24, 30, 36, 48];
d = diameter_range_data;
for h = height_range_data;
sigma_x_case1_it1 = (subs(sigma_x_case1))
end
Unrecognized function or variable 'sigma_x_case1'.
*** EDIT ***
*** Should be a 10 row (h) by 27 (d) table ***
sigma_x_case1 is a equation that was solved using other variables... would I need to convert this equation to a function (d, h) to perform the loop?
Please see the attached code for reference (Question_Thompson_Marshall_AENG_502_Project_Calcs.mlx) - All imshow functions commented out so the code can run.
The output of the for loop gives me the correct values when d and h are subbed into the equation using the "subs" function; however, the output gives the "sigma_x_case1_it1" variable 10 times and when I try to call it, it outputs the last iteration which indicates that it is writing over it (See Attached - Output.png). How do I get the for loop to output a 10x27 table or array that I can eventually write to Excel? Do I need to have the for loop output sigma_x_case1_it1 as 27 seperate variable then combine somehow in a matrix or table? If so, how do I do that or is there any easier way to solve this.
Any help would be appreciated!
Marshall
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Image Analyst el 3 de Dic. de 2023
What is sigma_x_case1?
Marshall Thompson el 3 de Dic. de 2023
sigma_x_case1 is an equation in terms of d and h that was solved with many other variables.

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Peter Perkins el 4 de Dic. de 2023
Marshall, the advice to try to vectorize is good advice, but if that's not possible, you might try something like at this:
height_range_data = linspace(2,3,10),
height_range_data = 1×10
2.0000 2.1111 2.2222 2.3333 2.4444 2.5556 2.6667 2.7778 2.8889 3.0000
diameter_range_data = [0.405,0.54,0.675,0.84,1.05,1.315,1.66,1.9,2.375,2.8753,5,4,4.5,5,5.563,6.625,8.625,10.75,12.75,14,16,18,20,24,30,36,48],
diameter_range_data = 1×27
0.4050 0.5400 0.6750 0.8400 1.0500 1.3150 1.6600 1.9000 2.3750 2.8753 5.0000 4.0000 4.5000 5.0000 5.5630 6.6250 8.6250 10.7500 12.7500 14.0000 16.0000 18.0000 20.0000 24.0000 30.0000 36.0000 48.0000
[h,d] = ndgrid(height_range_data,diameter_range_data);
h = h(:); d = d(:);
t = table(h,d)
t = 270×2 table
h d ______ _____ 2 0.405 2.1111 0.405 2.2222 0.405 2.3333 0.405 2.4444 0.405 2.5556 0.405 2.6667 0.405 2.7778 0.405 2.8889 0.405 3 0.405 2 0.54 2.1111 0.54 2.2222 0.54 2.3333 0.54 2.4444 0.54 2.5556 0.54
t2 = [t rowfun(@(h,d) h/d,t,OutputVariableName="Fun_hd")]
t2 = 270×3 table
h d Fun_hd ______ _____ ______ 2 0.405 4.9383 2.1111 0.405 5.2126 2.2222 0.405 5.487 2.3333 0.405 5.7613 2.4444 0.405 6.0357 2.5556 0.405 6.31 2.6667 0.405 6.5844 2.7778 0.405 6.8587 2.8889 0.405 7.1331 3 0.405 7.4074 2 0.54 3.7037 2.1111 0.54 3.9095 2.2222 0.54 4.1152 2.3333 0.54 4.321 2.4444 0.54 4.5267 2.5556 0.54 4.7325
You asked for a 10x27 array. You can easily turn this output into that, but depending on what you are doing after this, the above might (or might not) be a more convenient form.
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Marshall Thompson el 6 de Dic. de 2023
Thank you!
The output gives me a 270x3 table which is perfect for my analysis since that would be easiler to analyze the"Diameter Range" visually once I get the data to excel!
I am having trouble writing the table to excel...I am currently using these line of code to output the table and write to excel:
height_range_data = linspace(2, 3, 10);
diameter_range_data = [0.405, 0.54, 0.675, 0.84, 1.05, 1.315, 1.66, 1.9 ,2.375, 2.8753, 5, 4, 4.5, 5, 5.563, 6.625, 8.625, 10.75, 12.75, 14, 16, 18, 20, 24, 30, 36, 48];
[h,d] = ndgrid(height_range_data,diameter_range_data);
h = h(:);
d = d(:);
t = table(h,d);
sigma_x_iteration1 = [t rowfun(@(h,d) subs(sigma_x_case1),t,OutputVariableName="sigma_x_case1_it1")];
writetable(sigma_x_iteration1,excel_filename,"Sheet","Sigma_X (My) - IT 1");
The bolded line gives me an output table as shown in (Excel Table Output.png) where the sigma_x_case1_it1 values won't write to excel to Column C. I am confused since it is showing up in matlab as a 270x3 table so it should write the 3 coloumn of the table correctly but it seems like it is having issues with the values that are outputted from the subs(sigma_x_case1)? I've tried using "Range" in the writetable function as well as converting the 3rd column to an array using sigma_x_iteration{:,3} then back to table using array2table, then trying to writetable again but no luck.
Thanks!
Marshall Thompson el 6 de Dic. de 2023
Disregard!
double(subs(sigma_x_case1)) converted the 1x1 syms in the sigma_x_iteration1 output variable and I was able to write that to excel.
Thank you so much for the help @Peter Perkins
Marshall

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### Más respuestas (1)

Sulaymon Eshkabilov el 3 de Dic. de 2023
It can be computed using vectorization instead of loop - see this:
sigma_x_case1 = @(d, h)122.23*d.*(814.735*d+167.7312*h+335.4624) ./((d-1).^4-d.^4);
height_range_data = linspace(2, 3, 27);
h=height_range_data;
diameter_range_data = [0.405, 0.54, 0.675, 0.84, 1.05, 1.315, 1.66, 1.9 ,2.375, 2.8753, 5, 4, 4.5, 5, 5.563, 6.625, 8.625, 10.75, 12.75, 14, 16, 18, 20, 24, 30, 36, 48];
d = diameter_range_data;
[D, H] = meshgrid(d, h);
SS = sigma_x_case1(D,H);
surfc(D,H, SS)
xlabel('d')
ylabel('h')
zlabel('sigma_x_case1(d,h)')
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Marshall Thompson el 3 de Dic. de 2023
Editada: Marshall Thompson el 3 de Dic. de 2023
sigma_x_case1 is a equation based on many other variables so I can’t break it out and hard code the terms like you did since I will possibily need to change the input variables for futher analysis. Is there anyway I can apply the (d, h) to my sigma_x_case1 equation variable as a function and it will result in the same response?
Please see the attached file (Question_Thompson_Marshall_AENG_502_Project_Calcs.mlx) for all of the code.
Thanks

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