Error: Unable to perform assignment because the left and right sides have a different number of elements.

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Alexis Clark
Alexis Clark 2021-7-6
回答： Arthi Sathyamurthi 2021-7-20
At first I kept getting the error that the martix dimensions did not agree so I added the period before the operator "./" and now I am getting the error "Unable to perform assignment because the left and right sides have a different number of elements." I have attached my code below, the goal is to calculate strain with a changing diameter at an increment of 0.01.
F = 130;
Lb = 1.5;
T = (F * Lb) * 12;
M = T;
E = (9.863 * (10^6));
maxstrain = (1000 * (10^-6));
% Pipe Size 3
od3 = 3.5;
t3 = 0.216;
id3 = od3 - (2 * t3);
I3 = (pi / 4) * ((od3/2)^4) - ((id3)/2^4);
strain3 = (M * od3) / (2 * E * I3);
fprintf('The outer diamter for pipe size 3 is %.3f\n', od3)
fprintf('The strain for pipe size 3 is %.5f\n', strain3)
% Pipe Size 4
od4 = 4.5;
t4 = 0.237;
id4 = od4 - (2 * t4);
I4 = (pi / 4) * ((od4/2)^4) - ((id4)/2^4);
strain4 = (M * od4) / (2 * E * I4);
fprintf('The outer diamter for pipe size 4 is %.3f\n', od4)
fprintf('The strain for pipe size 4 is %.5f\n', strain4)
% Pipe Size 6
od6 = 6.625;
t6 = 0.280;
id6 = od3 - (2 * t6);
I6 = (pi / 4) * ((od6/2)^4) - ((id6)/2^4);
strain6 = (M * od6) / (2 * E * I6);
fprintf('The outer diamter for pipe size 6 is %.3f\n', od6)
fprintf('The strain for pipe size 6 is %.5f\n', strain6)
x = [od3, od4, od6];
y = [strain3, strain4, strain6];
subplot(2, 1, 1)
plot(x, y)
title('Outer Diamter vs Microstrain of Schedule 40 Pipe Sizes')
xlabel('Outer Diamter in inches')
ylabel('Microstrain')
inc = -0.01;
imax = 43;
din = od3;
d = zeros(43);
d = d(1:43);
I = zeros(43);
I = I(1:43);
for i = 1 : imax
d(i) = din - ((i-1).*inc);
I(i) = (M * dact) ./ (2 * E * I);
i = i + 1;
end
dact = d(:,1);
subplot(2, 1, 2)
plot(d, I)
  2 个评论
Alexis Clark
Alexis Clark 2021-7-6
CORRECTION: The equation is supposed to be I(i) = (M * d(i)) ./ (2 * E * I); I was playing around with it and forgot to switch it back before I posted. The errors are still the same regardless
Superficial
Superficial 2021-7-7
The reason you're getting that error is because Matlab is trying to fit 43 numbers (the result of the equation) into a space for a single number I(i).
Without knowing exactly what you're trying to achieve with the equation it's hard to know how to fix it. Perhaps you meant:
I(i) = (M * d(i)) ./ (2 * E * i); % (small i rather than I)
Your code is also kind of messy. I assume you've copied and pasted / adapted it rather than write it yourself? E.g:
d = zeros(43);
d = d(1:43);
For efficiency, should be replaced by:
d = zeros(1:43);
Also, you don't need the line
i = i+1
since your for loop will iterate that.

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回答（1 个）

Arthi Sathyamurthi
Arthi Sathyamurthi 2021-7-20
Hello Alexis,
The error has occurred because both sides of the equation doesn’t have equal number of elements. Hence, try replacing the lines from 48-57 with the following code
d = zeros(1,43);
I = zeros(1,43);
for i = 1 : imax
d(i) = din - ((i-1).*inc);
I(i) = (M * d(i)) ./ (2 * E * i);
end

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