Can Anyone Solve this error?

clc

% Part a

% ps1=exp (16.59158-(3643.31/(t-33.424)))

% ps2=exp (14.25326-(2665.54/(t-53.424)))

% T = 318.15 K and y1 = 0.60

t=318.15;

p=zeros(1,21);

syms y2 ps1 ps2 p x1 x2

for i=1:0.05:2

y1=i-1;

y2=1-y1;

k=round(((i-1+0.05)/0.05),0);

ps1 = exp (16.59158-(3643.31/(t-33.424)));

ps2 = exp (14.25326-(2665.54/(t-53.424)));

eqn1= p-((x1*ps1)+(x2*ps2))==0;

P(1,k)= vpa(solve(eqn1))

eqn2= x1-((y1*P(1,k))/ps1)==0;

X1(1,k)= vpa(solve(eqn2))

eqn3= x2-((y2*P(1,k))/ps2)==0;

X2(1,k)= vpa(solve(eqn3))

end

y1=0:0.05:1;

plot(y1,P,X1,P,'.-'), legend('y1vsP', 'X1vsP'),xlabel('x1,y1'), ylabel('P'), title('P vs xy Graph'),

grid on

Command Window:

Error using plot

Non-numeric data is not supported in 'Line'

Error in Examplethirteenpointone_b (line 24)

plot(y1,P,X1,P,'.-'), legend('y1vsP', 'X1vsP'),xlabel('x1,y1'), ylabel('P'), title('P vs xy Graph'),