Extract a row as a function of a variable

I have a numerical solution, which comes as a symbolic 6x51 matrix when I assign the values to T as T=[0:0.1:5].

I want to extract the first row (1x51) as a function of T, how to do it? The `rows2vars` prescription doesn't seem to work.

syms a T
v3=-2.375; g=1; b=0.00001; e2=0.5; k=pi/2;
w=-2*cos(k);
eqn = sin(3*k+a)/sin(2*k+a)==v3-w+(g.*T.^2)./(1+b.*T.^2)+(e2.*T.^2.*sin(k)^2)./(sin(2*k+a)^2+b*T.^2*sin(k)^2);
sol = solve(eqn,a,[0 pi]);
 solutions = vpa(subs(sol),3);
 xx=subs(solutions,T,[0:0.1:5])
%  xx(1,:)
T2 = rows2vars(xx); %does not work

Answer 1

[madhan ravi]

T=linspace(0,5,numel(xx(1,:)));
y=T.^2+sin(P+xx(1,:));
plot(T,y)

[AtoZ]

@madhan Thanks. Could you please specify your answer to the question? I am unable to understand your meaning, as I already used subs()..

[madhan ravi]

solve() doesn't solve your equation at all

[AtoZ]

This is running well on mine, could you try the following?

syms a T
v3=-2.375;
g=1;
b=0.00001;
e2=0.5;
k=pi/2;
w=-2*cos(k);
eqn = sin(3*k+a)/sin(2*k+a)==v3-w+(g.*T.^2)./(1+b.*T.^2)+(e2.*T.^2.*sin(k)^2)./(sin(2*k+a)^2+b*T.^2*sin(k)^2);
sol = solve(eqn,a,[0 pi]);

 solutions = vpa(subs(sol),3);
 xx=subs(solutions,T,[0:0.1:5])
 xx(1,:)

[madhan ravi]

Are you sure? because I get

Error using sym.getEqnsVars>checkVariables (line 92)
Second argument must be a vector of symbolic variables.

Error in sym.getEqnsVars (line 54)
    checkVariables(vars);

Error in solve>getEqns (line 429)
[eqns, vars] = sym.getEqnsVars(argv{:});

Error in solve (line 226)
[eqns,vars,options] = getEqns(varargin{:});

Error in COMMUNITY (line 9)
sol = solve(eqn,a,[0 pi]);

[AtoZ]

Sure, I get the result on R2014a as

xx = 0.0000000000058100074003806983143150013215135 + 0.0000000000022920983812460537064838532923356*i,..........

etc

[madhan ravi]

ok do one thing just attach your result as a text file here

[AtoZ]

Attached

[madhan ravi]

ok now we have xx what you want to do with it?

[AtoZ]

just extract the first row of it.. like xx(1,:), But as a function of T, because I want to use it to plot for T later.

[AtoZ]

If I can call it by something having T in it.. xx(1, something depending on T) if possible,,

[madhan ravi]

plot(T,real(xx(1,:)))  % because xx is complex so we plot T vs xx(1,:) or it's imaginary number 

[AtoZ]

Ok here's the situation:

I want to plot this first row, in a function involving T, so I want that when I give a range to T, say [0,5], then the function T.^2+sin(p+xx(1,f(T))) automatically leads to [0.5].^2+sin(p+xx(1,f([0,5]))) where f(T) is the first row in xx.

[madhan ravi]

Wait a minute.... where did you bring f from? what's f?

T=linspace(0,5,numel(xx(1,:)));
plot(T,xx(1,:))

[AtoZ]

No just to explain that the second argument in xx(1,:) should be a function of T, f(T) so I wrote xx(1,:)=xx(1,f(T)).

[madhan ravi]

T=linspace(0,5,numel(xx(1,:)));
y=T.^2+sin(P+xx(1,:));
plot(T,y)

[AtoZ]

@madhan Thanks :) Could you please update your answer?, I'll accept it.

[madhan ravi]

Anytime :) , updated my answer.