I don't know how to solve the error it is producing

P = 10; % kips
E = 30000; % ksi
H = 10; % feet
rho = 0.28; % lbm/in^3
db = [1.0, 6.0]; % inches - values of lower and upper bounds for db
tb = [0.01, 0.5]; % inches - values of lower and upper bounds for tb
numIters = 3;
segments = 15;
fun = @(b, t) cost(db, tb, P, E, H, rho, numIters, segments);
bounds = [db; tb];
Nvals = [10000];
for Ns=1:length(Nvals)
    [Jmin, xopt] = randsearch(fun, bounds, Ns);
end

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

Error in solution>randsearch (line 58)
Jout(n) = fun(grid(n,:));

%%      Functions
function [eigenVal, eigenVec] = PowerMeth(A, numIter)
eigenVec = ones(size(A, 1),1);
for i=1:numIter
    b = A*eigenVec;
    eigenVal = norm(b);
    eigenVec = b/eigenVal;
end
end
function Pcr = get_Pcr(ni, nn, E, d, t, H)
segments = nn-1;
h = H/segments;
A = full(spdiags([-1.0/h^2*ones(nn-2, 1), 2.0/h^2*ones(nn-2, 1), -1.0/h^2*ones(nn-2, 1)], [-1, 0, 1], nn-2, nn-2));
[eigenVal, eigenVec] = PowerMeth(inv(A), ni);
I = (pi.*((d+(2.*t)).^4-d.^4))/64;
Pcr = 1.0/eigenVal*E*I;
Ptrue = (pi^2*E*I)/(H^2);
if ((Ptrue-Pcr)/Ptrue)>0.01
    disp('Cant compute correctly')
end
end
function C = cost(d, t, P, E, H, rho, numIter, segments)
M = (pi.*t.*H.*rho).*(t+d);
Pcr = get_Pcr(numIter, segments, E, d, t, H);
if Pcr > P
    C = (2.*M)+(t.^-2);
else
    C = Inf;
end
end
function [Jmin, xopt] = randsearch(fun, bounds, Ns)
% Dimension of problem
nvar = length(bounds);
grid = zeros([Ns, nvar]);
Jout = zeros(Ns,1);
for k=1:nvar
    low = bounds(k,1);
    high = bounds(k,2);
    grid(:,k) = low + (high-low).*rand(Ns,1);
end

for n=1:Ns
    Jout(n) = fun(grid(n,:));
end

% Find index of max
[Jmin, idx] = min(Jout);
xopt = grid(idx,:);
end


%%          THIS IS THE ERROR
% Unable to perform assignment because the left and right sides have a
% different number of elements.
% 
% Error in HW6b>randsearch (line 69)
% Jout(n) = fun(grid(n,:));
% 
% Error in HW6b (line 20)
% [Jmin, xopt] = randsearch(fun, bounds, Ns);

[Les Beckham]

I'm not sure how you expect anyone to explain why Matlab is producing an error if you don't even tell us what the error is. Edit your question and copy and paste the entire error message (all of the red text). Also, select your code above and press the left hand button in the CODE section of the toolstrip to format the code. That will improve your chances of getting help.

[CONNOR]

Oh, I assumed that people just took the code and ran it themselves to see exactly what the issue is, but i included the error message at the bottom now.

[Les Beckham]

You have formatted one blank line as code. You must select the code (click and drag with the mouse) and then press the code formatting button.

Also, and more importantly, you still have not shown us the error message that you say you are getting -- all of the red text copied and pasted from your Command Window.

[CONNOR]

There I think I did it and the error is at the bottom of the code

[Dyuman Joshi]

@CONNOR, That's a fair assumption.

However, when we run the code provided, we might encounter some other or additional errors compared to error the poster gets. Sometimes there is some missing information, such as data files not available, variables not defined, etc etc.

Thus, to clarify, we ask the poster to copy and paste the full error message. And the error message also provides valuable information which aids in solving the issue, as the error message obtained here is not guaranteed to be exactly the same as the one encountered by the poster.

Answer 1

[Walter Roberson]

fun = @(b, t) cost(db, tb, P, E, H, rho, numIters, segments);

fun is a function that expects two parameters, and ignores both of them to call a function with constant inputs.

for n=1:Ns
    Jout(n) = fun(grid(n,:));
end

you are calling fun() with a single parameter that is a vector, rather than with two parameters.

But remember fun() ignores its inputs, so it does not matter what the parameter is.

What is important is that fun() is returning a non-scalar result.

[CONNOR]

so your saying where I have fun(grid(n,:)) it should say something like fun(d, t,

grid(n,:))?

[CONNOR]

Now its just saying Unrecocgnized function of variable 'd' or 't'