Need help! I keep getting the error "not enough input arguments" how do I fix this?

function drv = untitiled18(t,rv);

% small r is position
% big r is distance

mu = 3.986004*(10^5); %%unit is in km^3/s^2, and is Earth's Gravitational parameter

drv = zeros(6,1);

rx = rv(1);
vx = rv(2);
ry = rv(3);
vy = rv(4);
rz = rv(5);
vz = rv(6);

R = sqrt((rx^2)+(ry^2)+(rz^2));

% X component/ i direction

drv(1) = rv(2);
drv(2) = (-mu.*rx)/(R^3); % (vx) velocity in the x direction

% Y component/ j direction

drv(3) = rv(4);
drv(4) = (-mu.*ry)/(R^3); % (vy) velocity in the y direction

% Z component/ k direction

drv(5) = rv(6);
drv(6) = (-mu.*rz)/(R^3); % (vz) velocity in the z direction

end

[Steven Lord]

Please show the ode45 call that uses this function.

[Walter Roberson]

Do not invoke this with

ode45(untitled18, ....)

Instead you would need

ode45(@untitled18, ....)

[Denikka Brent]

So I've made some changes to the callouts. Here is my ode function:

function drv = propagate2BP(t,rv)

% small r is position
% big r is distance

mu = 3.986004*(10^5); %%unit is in km^3/s^2, and is Earth's Gravitational parameter

drv = zeros(6,1);

rx = rv(1);
vx = rv(2);
ry = rv(3);
vy = rv(4);
rz = rv(5);
vz = rv(6);

R = sqrt((rx^2)+(ry^2)+(rz^2));

% X component/ i direction

drv(1) = rv(2);
drv(2) = (-mu.*rx)/(R^3); % (vx) velocity in the x direction

% Y component/ j direction

drv(3) = rv(4);
drv(4) = (-mu.*ry)/(R^3); % (vy) velocity in the y direction

% Z component/ k direction

drv(5) = rv(6);
drv(6) = (-mu.*rz)/(R^3); % (vz) velocity in the z direction

end

Here is my script:

mu = 3.986004*(10^5); % unit is in km^3/s^2, and is Earth's Gravitational parameter  
ai = (15000+6378); % unit is in km
ei = .3;
ii = 10;
bigomegai = 0;
smallomegai = 10;
trueai = 0;
pi = ai.*(1-ei.^2);

velcompP = sqrt(mu/pi)*(-sind(trueai));
velcompQ = sqrt(mu/pi)*(ei+cosd(trueai));
velcompW = 0;
velpqw = [velcompP ; velcompQ ; velcompW];

rcompP = (pi*cosd(trueai)/(1+ei*cosd(trueai)));
rcompQ = (pi*sind(trueai)/(1+ei*cosd(trueai)));
rcompW = 0;
rpqw = [rcompP ; rcompQ ; rcompW];

IJKPQWrowtop = [(cosd(bigomegai)*cosd(smallomegai)-sind(bigomegai)*sind(smallomegai)*cosd(ii)) (-cosd(bigomegai)*sind(smallomegai)-sind(bigomegai)*cosd(smallomegai)*cosd(ii)) (sind(bigomegai)*sind(ii))];
IJKPQWrowmiddle = [(sind(bigomegai)*cosd(smallomegai)+cosd(bigomegai)*sind(smallomegai)*cosd(ii)) (-sind(bigomegai)*sind(smallomegai)+cosd(bigomegai)*cosd(smallomegai)*cosd(ii)) (-cosd(bigomegai)*sind(ii))];
IJKPQWrowbottom = [(sind(smallomegai)*sind(ii)) (cosd(smallomegai)*sind(ii)) cosd(ii)];
IJKPQW = [IJKPQWrowtop;IJKPQWrowmiddle ;IJKPQWrowbottom ];

Rvectori = IJKPQW*rpqw;
Vvectori = IJKPQW*velpqw;

vinputx = Vvectori(1); 
rinputx = Rvectori(1);
vinputy = Vvectori(2);
rinputy = Rvectori(2);
vinputz = Vvectori(3);
rinputz = Rvectori(3);
rimag = norm(Rvectori);
vimag = norm(Vvectori);

orbitalenergyi = ((vimag.^2)/2)-(mu/rimag);
tolerance = 1e-13;
t = [0 172800]; % unit is in seconds, 2 orbital periods is 2 days 
options = odeset('RelTol',tolerance,'AbsTol',tolerance);
[t,rv] = ode45(@propagate2BP, t, [rinputx, vinputx, rinputy, vinputy, rinputz, vinputz], options);

rxre = rv(:,1);
vxre = rv(:,2);
ryre = rv(:,3);
vyre = rv(:,4);
rzre = rv(:,5);
vzre = rv(:,6);

rrvector = [rxre ryre rzre]; 
rrtrans = (rrvector.');
vrvector = [vxre vyre vzre]; 
vrtrans = (vrvector.');

I am still getting the input issue. I would like to plot this orbit.

[Star Strider]

Your code (as you posted it in your most recent Comment) runs without error for me (in R2018a).

Plotting it with:

figure(1)
plot(t, rv)
grid

produces what appear to be reasonable results.

[Denikka Brent]

I am using R2017a. I don't think that would be the issue but I am upgrading the version now.

[Star Strider]

I agree. I doubt there are any significant differences between those versions with respect to ode45.

What line is throwing the error?

[Denikka Brent]

Not enough input arguments.

Error in propagate_2BP22 (line 11) rx = rv(1);

Error in untitled5 (line 41) [t,rv] = ode45(propagate_2BP22, t, [rinputx, vinputx, rinputy, vinputy, rinputz, vinputz], options);

Note: I did change the name again but the callouts match so that shouldn't be an issue.

Answer 1

[Star Strider]

Your latest code (as you posted it in your earlier Comment), runs for me without error.

The only thing I can think of is that you have a function called ‘rv’ somewhere. To find it, run this:

q = which('rv','-all')

[Denikka Brent]

I got the code to run. How can I subplot for velocity, position, and acceleration?

[Star Strider]

You could run your ‘propagate2BP’ function with the solved values to get some of those (I do not understand what variables those would be).

It would be easier to begin with the solved position values and use numerical differentiation one time to then get the velocity values, and two times to get acceleration.

Use the gradient (link) function to do the numerical differentiation. This will be more accurate if you define ‘t’ as:

t = linspace(0, 172800, 21681);

or something similar, to get equally-spaced solved position values.

In differentiating a matrix, gradient differentiates across both the rows and columns, and the first output is the derivative down the columns. I would do the differentiation as:

drv = gradient(rv, mean(diff(t)), 1);

Note that this differentiates all the columns, so choose the original position columns from the ‘drv’ output.

Answer 2

[Walter Roberson]

The error line you post is

[t,rv] = ode45(propagate_2BP22, t, [rinputx, vinputx, rinputy, vinputy, rinputz, vinputz], options);

which is not the same as what you posted before that, which was

[t,rv] = ode45(@propagate2BP, t, [rinputx, vinputx, rinputy, vinputy, rinputz, vinputz], options);

Notice the difference between propagate2BP and @propagate2BP . You need the @ version so your propagate_2BP22 would have to be @propagate_2BP22