What changes should have been made to run the code

%% HERE is the code
format long
wt=pi/2;    
t=1;
% t=0.01:0.01:5;
% w=pi/2;  
w=wt./t;
R=10;H=2;M=5;Kp=0.5;Gr=5;Gc=5;Kc=1;Pr=7;Sc=0.3; 
y=0:0.01:5;   
%  y=0; 
P1=abs(R-H); P2=M+(1/Kp);P3=sym(P2+1i*w);P4=sym(P2-1i*w);
P6=Gr/(P1-P2);P7=Gc/(Kc-P2);P5=(P6+P7);P8=(P1*Pr-P2)/(Pr-1);P9=Gr/(Pr-1);
P10=(Sc*Kc-P2)/(Sc-1);P11=Gc/(Sc-1);P12=-(P11/P10^2)-(P9/P8^2);P13=(P11/P10)+(P9/P8);

T1=(t+(y/2)*(sqrt(Pr/P1))).*exp(y*sqrt(Pr*P1)).*(1-erf((y/2).*sqrt(Pr./t)+sqrt(P1.*t))); 
T2=(t-(y/2)*(sqrt(Pr/P1))).*exp(-y*sqrt(Pr*P1)).*(1-erf((y/2)*sqrt(Pr./t)-sqrt(P1.*t)));
C1=(t+(y/2)*(sqrt(Sc/Kc))).*exp(y*sqrt(Sc/Kc)).*(1-erf((y/2)*sqrt(Sc./t)+sqrt(Kc.*t)));
C2=(t-(y/2)*(sqrt(Sc/Kc))).*exp(-y*sqrt(Sc/Kc)).*(1-erf((y/2)*sqrt(Sc./t)-sqrt(Kc.*t)));
T=(T1+T2)/2;C=(C1+C2)/2;

U1=exp(y*sqrt(P2)).*(1-erf(y./(2.*sqrt(t))+ sqrt(P2.*t)));
U2=exp(-y*sqrt(P2)).*(1-erf(y./(2.*sqrt(t))- sqrt(P2.*t)));
U3=exp(y*sqrt(P1*Pr)).*(1-erf((y./2)*sqrt(Pr./t)+ sqrt(P1.*t)));
U4=exp(-y*sqrt(P1*Pr)).*(1-erf((y./2)*sqrt(Pr./t)- sqrt(P1.*t)));
U5=exp(y*sqrt(Sc*Kc)).*(1-erf((y./2)*sqrt(Sc./t)+ sqrt(Kc.*t)));
U6=exp(-y*sqrt(Sc*Kc)).*(1-erf((y./2)*sqrt(Sc./t)- sqrt(Kc.*t)));
U7=exp(y*sqrt(P3)).*(1-erf(y./(2.*sqrt(t))+ sqrt(P3.*t)));
U8=exp(-y*sqrt(P3)).*(1-erf(y./(2.*sqrt(t))- sqrt(P3.*t)));
U9=exp(y*sqrt(P4)).*(1-erf(y./(2.*sqrt(t))+ sqrt(P4.*t)));
U10=exp(-y*sqrt(P4)).*(1-erf(y./(2.*sqrt(t))- sqrt(P4.*t)));

U=(P12/2).*(U1+U2)+(P13/2)*((t+(y/(2*sqrt(P2)))).*U1+(t-(y/(2*sqrt(P2)))).*U2)+((P9/(2*(P8^2))).*exp(-P8.*t)+(P11/(2*(P10^2))).*exp(-P10.*t)).*(U1+U2)+...
    (P9/(2*P8^2)).*(U3+U4)-(P9/(2*P8))*((t+(y/2)*sqrt(Pr/P1)).*U3+(t-(y/2)*sqrt(Pr/P1)).*U4)-(P9/(2*P8^2)).*exp(-P8.*t).*(U3+U4)+...
    (P11/(2*P10^2)).*(U5+U6)-(P11/(2*P10))*((t+(y/2)*sqrt(Sc/Kc)).*U5+(t-(y/2)*sqrt(Sc/Kc)).*U6)-...
    (P11/(2*P10^2)).*exp(-P10.*t).*(U5+U6) +exp(1i*wt)*(1/4).*(U7+U8)+exp(-1i*wt)*(1/4).*(U9+U10);

%% S1:  Partial derivative of 'U(t,y)' w.r.t 'y',  S2:  Partial derivative of 'T(t,y)' w.r.t 'y',
S1= - diff(U,y); 
S2= - diff(T,y);

v_t=0.01:0.01:5;
Sk = subs(S1,y,0);
Nu=subs(S2,y,0);
figure(1)
plot(v_t,vpa(subs(Sk,t,v_t)))
xlabel(' t');
ylabel('Sk');
hold on

figure(2)
plot(v_t,vpa(subs(Nu,t,v_t)))
xlabel(' t');
ylabel('Nu');
hold on
%%We need to draw graph of Partial derivative of 'U(t,y)' w.r.t 'y'   and  'T(t,y)' w.r.t 'y'     
at  y=0  for  t=0.01:0.01:5;

%% While running the code the following ERROR occurs:
Error using sym/diff (line 69)
The second argument must be a variable or a nonnegative integer specifying the number of differentiations.
Error in (line 37)
S1= - diff(U,y);

%%ANOTHER error for S2 is :
Error using diff
Difference order N must be a positive integer scalar.
Error in  (line 38)
S2= - diff(T,y);

[MINATI]

@ Thanks Madhan Ravi

Actually what is the procedure to place a code in this format?

And please if possible follow the code

[madhan ravi]

Anytime ,

1) Before pasting in the forum, select the code which is in MATLAB and then press ctrl + i which makes smart indent.

2) Copy that code , paste it here and you select the code.

3) Finally press the code button.

[MINATI]

Any help will be appreciated

[KALYAN ACHARJYA]

S1= - diff(U,y); 
%............^.....

Here the y value must be in integer as per diff definitions

Y = diff(X,n) calculates the nth difference by applying the diff(X) operator recursively n times.

In your case y is 1x501 double, therefore it reflect an error as below

Error using sym/diff (line 70)
Second argument must be a variable or a nonnegative integer specifying the number of differentiations.
Error in ans_may19 (line 37)
S1= - diff(U,y);

[MINATI]

@KALYAN ACHARJYA

So what changes should we do