Can someone please check my code, not quite sure where im going wrong

Question

Daniel Martelli 2020-9-22

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/597661-can-someone-please-check-my-code-not-quite-sure-where-im-going-wrong

关闭： MATLAB Answer Bot 2021-8-20

clc
clear
%--------------------------------------------------------------------------------------------------------%
p = 1.2;   %variables given to me in question
g = 9.81;
m = 77;
c = 1;
a1 = .7; 
a2 = 50; 
t1 = 50;
t2 = 70;
v0 = 50;
h0 = 2.5;
T = .005;
tmid = (t1+t2)/2; %formula gives to find what t mid is
%--------------------------------------------------------------------------------------------------------%
A = @(t) 1/2*(a2-a1)*tanh(10.*((t-tmid)/((t2-t1))))+(1/2*(a2+a1));
T1 = 0:1:120; %used for plotting x axis
D = @(T1)(p*c.*(A(T1)))/2*m; %drag constant
plot(T1, A(T1), 'b-', 50, .7, 'ro', 70, 50, 'ro') %t1 occurs at 50 seconds in, the area is .7 so I used that as a y co-ordinate and 50 as my x, marking that spot with a red circle.
axis([0 120, .6 70]); 
xlabel('Time')
ylabel('Area')
title('Area over Time')
%--------------------------------------------------------------------------------------------------------%
x(1) = 0;, vx(1) = v0;, y(1) = 0;, vy(1) = 0; %initial variables used to start the loop
for n=1 %initialize time index
    while 1 %forever while loop
        if y(n) > h0, break; end % break when ground is reached
        tn = (n-1)*T; %nth time instant in seconds
        t(n) = tn;  %build time vector, needed for plotting
        Dn = D(n).*(tn); %drag constant in time tn
        v = sqrt(vx(n)^2+vy(n)^2); %problem tells me to write "no need to save V in an array"- not sure what this means
        ax(n) = -Dn * vx(n)*v; %horizontal acceleration
        v(n) = sqrt(vx(n)^2+vy(n)^2); 
        ay(n)= -(D(tn)) * vy(n)*v(n)+g; ; 
        x(n+1) = x(n)+T*vx(n);
        vx(n+1)= vx(n)+T*ax(n);
        y(n+1)=y(n)+T*vy(n);
        vy(n+1)= vy(n)+T*ay(n);
        n = n+1; %updates the index to use N+1, so second round will use 2 for N, as N is defined as 1, N= 1+1, whill use 2 for N in next loop and so on. 
    end 
end
%--------------------------------------------------------------------------------------------------------%
Vc_1 = sqrt((2*m*g)/p*c*A(30));
Vc_2 = sqrt((2*m*g)/p*c*A(80));
Vc_3 = sqrt((2*m*g)/p*c*a1);
Vc_4 = sqrt((2*m*g)/p*c*a2);

8 个评论
显示 6更早的评论隐藏 6更早的评论

Image Analyst 2020-9-22

编辑：Image Analyst 2020-9-22

在 MATLAB Online 中打开

Your code does not crash. And MATLAB itself did not crash. Your code produced this plot:

clc
clear
%--------------------------------------------------------------------------------------------------------%
p = 1.2;   %variables given to me in question
g = 9.81;
m = 77;
c = 1;
a1 = .7; 
a2 = 50; 
t1 = 50;
t2 = 70;
v0 = 50;
h0 = 2.5;
T = .005;
tmid = (t1+t2)/2; %formula gives to find what t mid is
%--------------------------------------------------------------------------------------------------------%
A = @(t) 1/2*(a2-a1)*tanh(10.*((t-tmid)/((t2-t1))))+(1/2*(a2+a1));
T1 = 0:1:120; %used for plotting x axis
D = @(T1)(p*c.*(A(T1)))/2*m; %drag constant
plot(T1, A(T1), 'b-', 50, .7, 'ro', 70, 50, 'ro') %t1 occurs at 50 seconds in, the area is .7 so I used that as a y co-ordinate and 50 as my x, marking that spot with a red circle.
axis([0 120, .6 70]); 
xlabel('Time')
ylabel('Area')
title('Area over Time')
%--------------------------------------------------------------------------------------------------------%
x(1) = 0;, vx(1) = v0;, y(1) = 0;, vy(1) = 0; %initial variables used to start the loop
for n=1 %initialize time index
    while 1 %forever while loop
        if y(n) > h0, break; end % break when ground is reached
        tn = (n-1)*T; %nth time instant in seconds
        t(n) = tn;  %build time vector, needed for plotting
        Dn = D(n).*(tn); %drag constant in time tn
        v = sqrt(vx(n)^2+vy(n)^2); %problem tells me to write "no need to save V in an array"- not sure what this means
        ax(n) = -Dn * vx(n)*v; %horizontal acceleration
        v(n) = sqrt(vx(n)^2+vy(n)^2); 
        ay(n)= -(D(tn)) * vy(n)*v(n)+g; ; 
        x(n+1) = x(n)+T*vx(n);
        vx(n+1)= vx(n)+T*ax(n);
        y(n+1)=y(n)+T*vy(n);
        vy(n+1)= vy(n)+T*ay(n);
        n = n+1; %updates the index to use N+1, so second round will use 2 for N, as N is defined as 1, N= 1+1, whill use 2 for N in next loop and so on. 
    end 
end
%--------------------------------------------------------------------------------------------------------%
Vc_1 = sqrt((2*m*g)/p*c*A(30));
Vc_2 = sqrt((2*m*g)/p*c*A(80));
Vc_3 = sqrt((2*m*g)/p*c*a1);
Vc_4 = sqrt((2*m*g)/p*c*a2);

Daniel Martelli 2020-9-23

It did crash, but once i saved the worked it didnt crash

Image Analyst 2020-9-23

Saving the m-file won't prevent the script from throwing an error. If it's not saved, it will actually ask you to save the file before it runs even the first line of the script. So it can't crash before it's saved. However, we're glad its working (for whatever reason) now.

此问题已关闭。

Can someone please check my code, not quite sure where im going wrong

8 个评论
显示 6更早的评论隐藏 6更早的评论

回答（0 个）

另请参阅

标签

Community Treasure Hunt

Can someone please check my code, not quite sure where im going wrong

8 个评论 显示 6更早的评论隐藏 6更早的评论

回答（0 个）

另请参阅

标签

Community Treasure Hunt

8 个评论
显示 6更早的评论隐藏 6更早的评论