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Not enough input arguments

Asked by Andrea Giordano on 11 Mar 2019
Latest activity Commented on by Adam Danz
on 11 Mar 2019
Hello there!
I am writing a simple function but I can not understand why it will not work.
The error says "Not enough input arguments", right when the compiler is compiling the function I called ecc_anomaly.
Could you help me? I know the code is banal, though I can not fix it!
Thank you in advance!
The infamous function
function E = ecc_anomaly(tow, toe, GM, sqrta, M0, ecc)
i = 0;
M = M0+(tow-toe)*sqrt(GM/sqrta^6);
a = M0;
while i >= 10^-13
E = M0+ecc*sin(a);
i = abs(E-a);
a = E;
end
end
And finally my main
clc
clear all
format long
GM = 3.986005e14; % m^3/s^2
rotation = 7.2921151467e-5; % rad/s
tow = 223221; % s (self-check value)
%tow = 225445; % s
M0 = 1.94850072201; % rad
sqrta = 0.544062105942e+04; % m^0.5
ecc = 0.404827296734e-04; % unitless
toe = 0.225600000000e+06; % s
E = ecc_anomaly(tow, toe, GM, sqrta, M0, ecc);
f = t_a(ecc, E);
r = sqrta^2*(1-ecc*cos(E));
x_1 = r*cos(f);
x_2 = r*sin(f);

  3 Comments

Can you show us the exact text of the error message (everything displayed in red text)? The exact text will likely include more information about the specific location where the error occurs.
Though I wouldn't have expected the error you received; when I ran the code it gave me a different error. Inside your ecc_anomaly function you start off with i equal to 0 and then loop while i is greater than or equal to 1e-13. Since 0 is not greater than or equal to 1e-13, MATLAB never enters the while loop and so E is never assigned a value. So there may be some difference between the code you're running and the code you posted. Can you confirm that you copied and pasted both those pieces of code directly from the Editor into Answers?
I can confirm this, but the function got somehow wrong. "i" should be set to one at the beginning. Here the correct version. Apologies.
function E = ecc_anomaly(tow, toe, GM, sqrta, M0, ecc)
i = 1;
M = M0+(tow-toe)*sqrt(GM/sqrta^6);
a = M0;
while i >= 10^-13
E = M0+ecc*sin(a);
i = abs(E-a);
a = E;
end
end
Here the error message
>> ecc_anomaly
Not enough input arguments.
Error in ecc_anomaly (line 3)
M = M0+(tow-toe)*sqrt(GM/sqrta^6);
This version does not produce an error within the ecc_anomaly() funciton. It returns
E = 1.948538350699015

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2 Answers

Answer by Steven Lord
on 11 Mar 2019
 Accepted Answer

Your function is declared to accept six input arguments:
function E = ecc_anomaly(tow, toe, GM, sqrta, M0, ecc)
When you call it, you need to pass six inputs into it. When you try to call it with zero inputs like:
>> ecc_anomaly
MATLAB doesn't know what value to use as M0 on that line of code. It also doesn't know what values to use for tow, toe, GM, and sqrta, but M0 is the first variable it "sees" on that line.
There are ways to specify default values for when you call the function with fewer inputs than it's declared to accept (using functions like nargin) but easier is to call it with six inputs as you do in the "main" in the original message. I couldn't run your full "main" code since I don't have the t_a function, but I was able to run up through the ecc_anomaly call it contains.

  1 Comment

Note that there are no errors when the function is called properly from within the script provided.
clc
clear all
format long
GM = 3.986005e14; % m^3/s^2
rotation = 7.2921151467e-5; % rad/s
tow = 223221; % s (self-check value)
%tow = 225445; % s
M0 = 1.94850072201; % rad
sqrta = 0.544062105942e+04; % m^0.5
ecc = 0.404827296734e-04; % unitless
toe = 0.225600000000e+06; % s
E = ecc_anomaly(tow, toe, GM, sqrta, M0, ecc);
f = t_a(ecc, E);
r = sqrta^2*(1-ecc*cos(E));
x_1 = r*cos(f);
x_2 = r*sin(f);
function E = ecc_anomaly(tow, toe, GM, sqrta, M0, ecc)
i = 1;
M = M0+(tow-toe)*sqrt(GM/sqrta^6);
a = M0;
while i >= 10^-13
E = M0+ecc*sin(a);
i = abs(E-a);
a = E;
end
end

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Answer by Guillaume
on 11 Mar 2019

>> ecc_anomaly
Calls ecc_anomaly with no inputs argument. So, yes, you will get a "Not enough input arguments." error.
I'm not sure what else you expected to happen when you wrote that. Considering that you wrote: "right when the compiler is compiling the function I called ecc_anomaly", maybe you expected it to somehow compile the function. Base matlab does not include a compiler and if you do have matlab compiler, that's certainly not the way to go. The above simply call the function.

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