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

Hi guys,

I need some help with the following code:

function xd=f1(t, x, YH, YA, fp, iXB, miuH, bH, KS, KOH, KNO, miuA, bA, KOA, KNH, niug, ka, kh, KX, niuh)
...
   Xset =0.2;
er  = x(3)-Xset;
Ds= Kp*er + Ki*x(14);
...
    xd(3)=-(1/YH)*(p1+p2)+p7+Ds*SSin-Ds*x(3);      
...
    xd(14)=er;
Script:
global D SSin XSin XPin XNDin SNDin SNHin SNOin SOin SALKin alpha W Ssat Kp Ki
    ...
Tu = Y*2.6;
Ku = W-SSin;
Kp = 0.45*Ku;
Ki = 0.54*Ku/Tu;

...
x0=[10 10 2*30 2*70 0 1 1 10 2 2  10 0 0 0];
...

I have this error:

Error in f1 (line 37)

xd(3)=-(1/YH)*(p1+p2)+p7+Ds*SSin-Ds*x(3); % SS

Error in

script>@(t,x)f1(t,x,YH,YA,fp,iXB,miuH,bH,KS,KOH,KNO,miuA,bA,KOA,KNH,niug,ka,kh,KX,niuh)

(line 57)

[t,x]=ode45(@(t,x)f1(t,x, YH, YA, fp, iXB, miuH, bH, KS, KOH, KNO, miuA,

bA, KOA, KNH, niug, ka, kh, KX, niuh), [t0 tf], x0);

Can you help me, please?

Thanks!

[Tayyab Khalil]

How many elements do you expect to have in xd? Initialize it accordingly with zeroes.

[Mihaela Lazar]

14 elements

[Mihaela Lazar]

I did it but nothing happend

Answer 1

[Walter Roberson]

One of your global variables is not initialized.

Avoid using global variables.

https://www.mathworks.com/help/matlab/math/parameterizing-functions.html