Error in Function ?

[t,v] = ode45(@velocity, [10 1], [22.5])
     plot(t,c)
function f = velocity(t,v)
 f = 8*v/t
 M = [4 5;5 6]
 K = [23 45;67 54]
 [X e] = polyeig(K,M)
 F = [32+f;32+f]
 wn = 3221.3;
zeta = 0.061;
wd = 3254.4;
Fn = X.'*F
Fnn = Fn(2,1)
g = -wd.^2*sin(wd*t) - 2*wd*zeta*wn*cos(wd*t) +zeta.^2*wn.^2*sin(wd*t)
a = Fnn.*(cos(-zeta*wd*t)+sin(-zeta*wd*t))/(8*wd.^2 +1i*2.12*wd+253)
c = a.*g
end

From the above code I am getting this error" Data must be numeric, datetime, duration or an array convertible to double". so,help me to plot t with c .Thank you in advance.

Answer 1

[Walter Roberson]

     plot(t,c)

You are not storing into c in the workspace that you are doing the ode45 call, so it will have whatever value it had before the call.

function f = velocity(t,v)
 f = 8*v/t
 M = [4 5;5 6]
 K = [23 45;67 54]
 [X e] = polyeig(K,M)
 F = [32+f;32+f]
 wn = 3221.3;
zeta = 0.061;
wd = 3254.4;
Fn = X.'*F
Fnn = Fn(2,1)
g = -wd.^2*sin(wd*t) - 2*wd*zeta*wn*cos(wd*t) +zeta.^2*wn.^2*sin(wd*t)
a = Fnn.*(cos(-zeta*wd*t)+sin(-zeta*wd*t))/(8*wd.^2 +1i*2.12*wd+253)
c = a.*g
end

The only line there that affects the ode45 integration is the very first one, f = 8*v/t . All of the rest are wasted computation as far as ode45 is concerned.

I would suggest,

[t,v] = ode45(@velocity, [10 1], [22.5]);
c = arrayfun(@calc_c, t, v);
plot(t, c);

function f = velocity(t,v)
  f = 8*v/t;
end

function c = calc_c(t,v)
  f = 8*v/t;
  M = [4 5;5 6];
  K = [23 45;67 54];
  [X e] = polyeig(K,M);
  F = [32+f;32+f];
  wn = 3221.3;
  zeta = 0.061;
  wd = 3254.4;
  Fn = X.'*F;
  Fnn = Fn(2,1);
  g = -wd.^2*sin(wd*t) - 2*wd*zeta*wn*cos(wd*t) +zeta.^2*wn.^2*sin(wd*t);
  a = Fnn.*(cos(-zeta*wd*t)+sin(-zeta*wd*t))/(8*wd.^2 +1i*2.12*wd+253);
  c = a.*g;
end

[naresh bhimchand]

Thanks for your valuable feedback bro.

[naresh bhimchand]

I have another doubt in this code bro. Instead of using timespan [10 1] i like to use [10:0.0001:0], but i cannot able to proceed that increment.Can you help with any syntax for that, bro?

[Steven Lord]

You can't get from 10 to 0 by taking steps of length 0.0001.

You can get from 10 to 0 by taking steps of length -0.0001.

[naresh bhimchand]

Sorry my mistake.Thanks,bro.