Error in ODE45 function

When I type up this code, I keep getting that there is an undefined variable, however, the variable is defined and I do not know what is happing. Here is the erro I am recieving:

Undefined function or variable 'dt'.

Error in Homework3_solutioncode2018>pose_dot (line 68)

ind = floor(t/dt) + 1;

Error in odearguments (line 90)

f0 = feval(ode,t0,y0,args{:}); % ODE15I sets args{1}

to yp0.

Error in ode45 (line 115)

odearguments(FcnHandlesUsed, solver_name, ode, tspan,

y0, options, varargin);

Error in Homework3_solutioncode2018 (line 30)

[t_out,Xi] = ode45(@pose_dot,[T_init T_final],dt,Xi_0);

Here is my overall code:

clc;
clear all;
close all;

VarInput = load('Hw3_quadData.mat');
qDat = VarInput.quadrotor;
[n,~] = size(qDat);                  % n is the number of timesteps

% Extract the initial condition, and body rate info, and time info

Xi_0 = [qDat(1,2:4)'; qDat(1,8:10)'];
v = qDat(:,5:7);
omega = qDat(:,11:13);
t = qDat(:,1);
dt = qDat(2,1) - qDat(1,1);
T_init = qDat(1,1);
T_final = qDat(end,1);

% Call pose_dot once to initialize persistant variables
pose_dot(1,Xi_0,{dt,v,omega});

% Call ODE 45 to integrate for Xi = [x,y,z,phi,theta,psi]
[t_out,Xi] = ode45(@pose_dot,[T_init T_final],Xi_0);

% Plot solutions and truth values
% Euler Angles
figure(1)
plot(t_out,Xi(:,4:6)*(180/pi),':');
hold on
plot(t,qDat(:,8:10)*(180/pi),'--');
legend('\phi_{calc}','\theta_{calc}','\psi_{calc}','\phi_{true}','\theta_{true}','\psi_{true}');
grid on
title('Euler Angles vs. Time');
ylabel('Euler Angles (Degrees)');
xlabel('Time (Seconds)');

% Position
figure(2)
plot(t_out,Xi(:,1:3),':');
hold on
plot(t,qDat(:,2:4),'--')
legend('x_{calc}','y_{calc}','z_{calc}','x_{true}','y_{true}','z_{true}');
grid on
title('CoM Position vs Time');
ylabel('Position (meters)');
xlabel('Time (seconds)');

function Xi_dot1 = pose_dot(t,Xi,prstVars)

% Declare persistant variables that will remain between function calls
% persistant dt v omega

if nargin > 2
    dt = prstVars{1};
    v = prstVars{2};
    omega = prstVars{3};
end

% Find values the aircraft velocity in the body frame and the body angular
% rates for time t.
ind = floor(t/dt) + 1;
nu = [v(ind,:)'; omega(ind,:)'];

% Find trig values for neater presentation of kinematic equations below:
cPsi = cos(Xi(6));
sPsi = sin(Xi(6));
cPhi = cos(Xi(4));
sPhi = sin(Xi(4));
cTh = cos(Xi(5));
sTh = sin(Xi(5));
tTh = tan(Xi(5));

Xi_dot1 = [cPsi*cTh cPsi*sTh*sPhi-sPsi*cPhi sPsi*sPhi+cPsi*sTh*cPhi 0 0 0;...
           sPsi*cTh cPsi*cPhi+sPsi*sTh*sPhi sPsi*sTh*cPhi-cPsi*sPhi 0 0 0;...
           -sTh cTh*sPhi cTh*cPhi 0 0 0;...
           0 0 0 1 sPhi*tTh cPhi*tTh;...
           0 0 0 0 cPhi -sPhi;...
           0 0 0 0 sPhi/cTh cPhi/cTh]*nu;
end

quadData is a 1759x13 array

Answer 1

[Walter Roberson]

You have

% persistant dt v omega

where the statement is commented out. You need to uncomment and fix the spelling:

persistent dt v omega

However, we would recommend that you not do this trick of initializing variables by calling once with extra arguments. Instead see http://www.mathworks.com/help/matlab/math/parameterizing-functions.html