Invalid indexing or function definition.

clc;
clear all; 
close all;
syms y1(t) y2(t) y3(t) y4(t) y5(t) y6(t) y7(t) y8(t) 
C = 3*10^10;
KT = 0.086173324;  % MeV
M0 = 1.0078;       % u
M1 = 1.0078;       % u
M2 = 2.014102;     % u
M3 = 1.0078;       % u
M4 = 2.014102;     % u
M5 = 2.014102;     % u
M6 = 3.016030;     % u
M7 = 2.014102;     % u
M8 = 3.016030;     % u
M9 = 3.016030;     % u
M10 = 3.016030;    % u
M11 = 4.002603;    % u
Z0 = 1;  
Z1 = 1;  
Z2 = 1;  
Z3 = 1;
Z4 = 1;  
Z5 = 1;  
Z6 = 2;  
Z7 = 1;
Z8 = 2;  
Z9 = 2;
Z10 = 2;
Z11 = 2;

Eat = 0.98951013;
m01 = (M0*M1)/(M0+M1);
m23 = (M2*M3)/(M2+M3);
m45 = (M4*M5)/(M4+M5);
m67 = (M6*M7)/(M6+M7);
m89 = (M8*M9)/(M8+M9);
m1011 = (M10*M11)/(M10+M11);

cont = (931.494)./(3*10^10)^2;
cont1 = 10^-24;

sy0 = 0.1; 
Q2 = (4.08*10^-15)*((y8./KT)^(-2/3))*exp(-3.381*((y8./KT)^(-1/3)))*(1+(3.82*y8./KT)+1.51*((y8./KT)^2)+0.144*(y8./KT)^3-1.14*(10^-2)*(y8./KT)^4)./(6.023*10^23);
Q4 =(2.58*10^3)*((y8./KT)^(-2/3))*exp(-3.721*((y8./KT)^(-1/3)))*(1+(3.96*y8./KT)+0.116*(y8./KT)^2)./(6.023*10^23);
Q5 = ((5.59*10^10)*(((y8./KT))^(-2/3))*exp(-12.277*((y8./KT)^(-1/3)))*(1-0.135*(y8./KT)+2.54*0.01*((y8./KT)^2)-1.29*0.001*((y8./KT)^3)))./(6.023*10^23);
D = (2.07*10^14)*((y8./KT)^(3/2))*(1-0.860*((y8./KT)^(1/2))+0.429*(y8./KT))*exp(-25.82/(y8./KT));

nB = (0.6*10^-9)*(((2*1.202)./(pi.^2))*(((10^6)*sy0.*8065.73).^3));
nP = 0.75*nB;
nN = 0.25*nB;
nEn = ((((3*1.202)./(2*pi.^2))*(((10^6)*sy0.*8065.73).^3)))+ nP;
nEp = ((((3*1.202)./(2*pi.^2))*(((10^6)*sy0.*8065.73).^3)))*(exp((-0.511)./(sy0)));
Wtn2 = 1000;
Wconst2 = ((1.239*10^-10)^3);
Wb2 = ((7.56*10^-16)*((1.239*10^-6)^3))./((1.6*10^-19)*((8.617*10^-5)^4));
WV2 = (3*10^10)*sqrt(1-(1./((y8/0.511)+1))^2);
WF2 = (((1.166*10^-23)./(8065.73*10^6))^2)*((y8)^2)*(exp(-(0.783)./y8)); 
WF1 = (((1.166*10^-23)./(8065.73*10^6))^2)*((y8)^2);
L1 = (y3./Wtn2)+(y5*D)-(y1*y4*WF2*WV2)-(y1*y2*WF1*WV2);
L2 = (((y4)^2)*Q2*0.5)-(y2*y3*WF1*WV2)-(y1*y2*WF1*WV2);
L3 = (y1*y4*WF2*WV2)+(y5*D)-(y2*y3*WF1*WV2)-(y3./Wtn2);
L4 = (y3./Wtn2)+(y2*y3*WF1*WV2)+(y5*D)+(((y6)^2)*Q5)-(y1*y4*WF2*WV2)-(((y4)^2)*Q2*0.5)-(y4*y5*Q4);
L5 = (((y4)^2)*Q2*0.5)-(y5*D)-(y4*y5*Q4);
L6 = (y4*y5*Q4)-(((y6)^2)*Q5*0.5);
L7 = (((y6)^2)*Q5*0.5);
S1 = (((((y4)^2)*Q2*0.5)*1.44)-((y5*D)*2.22)+((y4*y5*Q4)*5.49)+((((y6)^2)*Q5*0.5)*12.86));
S2 = (((y2*y3*WF1*WV2))+((y1*y4*WF2*WV2))+(2*(y1*y2*WF1*WV2))+((y3./Wtn2))+((((y4)^2)*Q2*0.5)))*y8;
L8 = ((Wconst2).*(S1-S2))./(4*Wb2.*((y8)^3));
ode1 = diff(y1)==L1;
ode2 = diff(y2)==L2;
ode3 = diff(y3)==L3;
ode4 = diff(y4)==L4;
ode5 = diff(y5)==L5;
ode6 = diff(y6)==L6;
ode7 = diff(y7)==L7;
ode8 = diff(y8)==L8;
odes = [ode1;ode2;ode3;ode4;ode5;ode6;ode7;ode8];
% S = dsolve(odes)
cond1 = y1(0)==nEn;
cond2 = y2(0)==nEp;
cond3 = y3(0)==nN;
cond4 = y4(0)==nP;
cond5 = y5(0)==0;
cond6 = y6(0)==0;
cond7 = y7(0)==0;
cond8 = y8(0)==0.1;
conds = [cond1;cond2;cond3;cond4;cond5;cond6;cond7;cond8];
[y1Sol(t),y2Sol(t),y3Sol(t),y4Sol(t),y5Sol(t),y6Sol(t),y7Sol(t),y8Sol(t)] = dsolve(odes,conds);

Warning: Unable to find symbolic solution.

Error using sym/subsindex (line 953)
Invalid indexing or function definition. Indexing must follow MATLAB indexing. Function arguments must be symbolic variables, and function body must be sym expression.

t = linspace(10^-25,10^-22,10);
loglog(t,y1Sol(t),'k-','linewidth',2)

Answer 1

[Cris LaPierre]

Remove the (t) from the output variables for dsolve. It is treating t as an index.

[y1Sol,y2Sol,y3Sol,y4Sol,y5Sol,y6Sol,y7Sol,y8Sol] = dsolve(odes,conds);

[mohamed elkasemy]

Thanks..Cris LaPierre

I have problem with

Error using loglog

Vectors must be the same length.

[Cris LaPierre]

The reason is because of the warning message that is still there (Unable to find symbolic solution). t is a 1x10 vector, but y1Sol is an empty vector.