Numercial Iterations using Loop
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function [vAn,vNum] = Q3_STNO(T,N,m,d)
T = 5
N = 10
m = 5
d = 0.5
Cd = 0.47
p = 1.2
A = (pi)*((d/2)^2);
g = 9.81;
Terminal_V = -sqrt((2*m*g)/p*Cd*A)
V= -Terminal_V*tanh(g*T/Terminal_V)
acc = (((Cd*p*A)/2*m))*(V^2)-g
for acc = 1:1:T
V = V + acc*(T/N)
plot(T,V)
end
end
I have written my codes several times , its been 1 week now and I still cannot get the code to work. Any help would be extremely appreciated.
Seif
3 个评论
Jan
2019-1-23
We cannot guess, what the problem is. Please explain, what "cannot get code to work" means. What do you want to achieve and what is not working yet?
Image Analyst
2019-1-23
You need "hold on" after the call to plot. And you need to plot (acc, V) to plot that point, NOT plot(T, V). There may be other problems but that's what I saw off the top of my head.
Seif Eldein Zahran
2019-1-23
采纳的回答
Jan
2019-1-23
This is strange:
function [vAn,vNum] = Q3_STNO(T,N,m,d)
You do not create the outputs vAn and vNum. The inputs T,N,m,d are overwritten immediately, then it is better to omit them. Or define them by using the inputs, as mentioned in the question.
function Main
T = 5; % Trailing semicolons suppress the output to the command window
N = 10;
m = 5;
d = 0.5;
[vAn,vNum] = Q3_STNO(T,N,m,d)
end
function [vAn, vNum] = Q3_STNO(T,N,m,d)
Cd = 0.47;
p = 1.2;
A = pi *(d/2)^2; % Do not use too many parentheses
g = 9.81;
vEnd = -sqrt(2 * m * g / (p * Cd * A)); % Here you need parentheses
% around the denominator
vAn = -Terminal_V * tanh(g * T / Terminal_V);
% The acceleration is not fixed, so you need it inside the loop:
% acc = (((Cd*p*A)/2*m))*(V^2)-g
% In addition: Missing parentheses around (2*m)!
% It is not the acceleration which goes from 1 to T
% for acc = 1:1:T
% You need T/N steps for the time. Usually the time starts at 0.
V = 0; % what is the initial velocity?
plot(0, V, '.');
hold on
for t = 0:T/N:T
acc = Cd * p * A / (2 * m) * V^2 - g;
V = V + acc * (T / N);
plot(t, V);
end
vNum = V;
end
You need some more details according to the question, and I leave this up to you.
更多回答（3 个）
Seif Eldein Zahran
2019-1-23
0 个投票
1 个评论
Image Analyst
2019-1-24
Since your T and V were just scalars, not arrays, plot(T, V) will plot just a single point. However each call to plot blows away everything prior and plots only the current points. To have it not blow away prior things that were plotted, you need to put hold on. If you call hold on after plot() then your prior points will remain and you will see all of them
If you're in a loop, the message to update/refresh the plot will probably not be acted upon until the loop is finished. If you want to see every point as it's plotted you might want to call drawnow() followed by a pause() to slot it down enough that it looks like an animation:
for index = 1 : T
V = V + ....whatever
T = ....... whatever
plot(T,V); % Plot one single point.
hold on; % Don't blow away prior points.
drawnow; % Force screen to refresh immediately instead of after loop.
pause(0.5); % Wait long enough so that points are plotted slowly and it looks like an animation.
end
Image Analyst
2019-1-23
Here is a bit closer. Still not right yet, but closer. If you still can't complete it, let us know.
% Call the function from the main routine
T = 5
N = 10
m = 5
d = 0.5
[vAn,vNum] = Q3_STNO(T,N,m,d)
% Define the function that the main routine will call.
function [vAn,vNum] = Q3_STNO(T,N,m,d)
vAn= 0; % Initialize
vNum = 0; % Initialize
Cd = 0.47
p = 1.2
A = (pi)*((d/2)^2);
g = 9.81;
Terminal_V = -sqrt((2*m*g)/p*Cd*A)
V(1) = -Terminal_V*tanh(g*T/Terminal_V)
acc = (((Cd*p*A)/2*m))*(V^2)-g
for index = 2 : T
V(index) = V(index-1) + acc * (T/N)
end
index = 1 : T;
plot(index, V, 'b+-', 'LineWidth', 2, 'MarkerSize', 15)
xlabel('index', 'FontSize', 14);
ylabel('V', 'FontSize', 14);
grid on;
end
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