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

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)

[Alexis Clark]

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]

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.

Answer 1

[Arthi Sathyamurthi]

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