Error - Vectors must be the same length

Hi everyone,

This is very wierd.

I entered this code to plot a (epscmv, cdivd) graph and there are two problems:

1) sometimes it works and draws the graph but most of the time it errors:

Error using plot
Vectors must be the same length.

Error in Untitled (line 30)
plot(epscmv, cdivd

2) the graph has to finish at epsAtMmax which is 2.7671 but it stoppes at 3.5 instead..

Thank you for your help.

b=300;  %mm
d=400;  %mm
fc=40;  %Mpa
Ecm=22*(fc/10)^0.3*10^3;  %Mpa
Es=200000;  %Mpa
As=2400;  %mm^2
fy=400;  %Mpa
epsc1=min(2.8/1000,0.7*fc^0.31/1000);
epscu=3.5/1000;
k=1.05*Ecm*epsc1/fc;

epscmv = linspace(0.05, 3.5, 500)*1E-3;
for i=1:numel(epscmv);
    epscm = epscmv(i);
    funC=@(epsc) (k*epsc/epsc1-(epsc/epsc1).^2)./(1+(k-2)*epsc/epsc1);
    compression=@(c) b*fc*c/epscm*integral(funC,0,epscm)/1000;
    tension=@(c) min(Es*(d-c)/c*epscm*As/1000,fy*As/1000);
    c(i)=fsolve(@(c) compression(c)-tension(c),1);
    funM=@(epsc)(k*epsc./epsc1-(epsc./epsc1).^2)./(1+(k-2)*epsc./epsc1).*(d-c(i)+(c(i)./epscm).*epsc); 
    M(i)=b*fc*c(i)/epscm*integral(funM,0,epscm)/1000000;
    phi(i)=epscm/c(i);
    cdivd(i)=c(i)/d;
    if (i > 1) & (M(i)<M(i-1))
        break;
    end
end

[Mmax,idx]=max(M) %[kNm]
phiAtMmax=phi(idx)  %[1/mm]
epsAtMmax=epscmv(idx)*1000  %[promil]


plot(epscmv, cdivd)
grid on
xlabel('epsilon cm')
ylabel('c/d')

[Shimon Katzman]

Please HELP

Answer 1

[Star Strider]

Your code does what you want it to, including the if block, and appears to produce the desired results:

Mmax =
          342.497032418162
idx =
   394
phiAtMmax =
      2.50775914909749e-05
epsAtMmax =
          2.76713426853707

Solve the plot error by limiting the ranges on both arguments:

plot(epscmv(1:idx), cdivd(1:idx))

That worked when I ran it, and the plot stops at the appropriate value of ϵ. Your code does what you want it to, including the if block, and appears to produce the desired results:

Mmax =
          342.497032418162
idx =
   394
phiAtMmax =
      2.50775914909749e-05
epsAtMmax =
          2.76713426853707

Solve the plot error by limiting the ranges on both arguments:

plot(epscmv(1:idx), cdivd(1:idx))

That worked when I ran it, and the plot stops at the appropriate value of ϵ.

[Shimon Katzman]

Star THANK YOU VERY MUCH!!!!

YOU DEFIENETLY THE BEST!

[Star Strider]

As always, my pleasure!

I very much appreciate your compliments!

[Shimon Katzman]

Hi Star,

Can yoy please help me in the following link? I think you the only person in the world that can help me..

Thank you very much.

https://www.mathworks.com/matlabcentral/answers/493112-error-undefined-function-or-variable#answer_403289?s_tid=prof_contriblnk

[Star Strider]

As always, my pleasure!

Please see my Answer.