How do I input the y-coordinate as a variable in Matlab?

I have to input a function where the output is reliant on the y-axis coordinate

Uwind = -75*(1-((75-y)/75)^2)

Is there any way that i can make the y value the y coordinate at any given point along the x axis?

[madhan ravi]

Your code for better understanding.

Answer 1

[madhan ravi]

syms y
Uwind = -75*(1-((75-y)/75)^2)
fplot(Uwind)

is this what you are looking for ? if not let know

[John Rae]

I don't think this is it. Later in my code when I use an i loop I get an error message saying that it can't convert the syms value to double form

[madhan ravi]

That’s why I told you upload the full code

[John Rae]

m=0.05 %kg
A=pi*(.03)^2 %m^2
C=0.8 
U=50 %m/s
density= 1.183 %kg/m^3 
D=0.5*density*C*A^2*sign(U) %N
g=9.81 %m/s^2 
theta=25 %deg
Uwind = -75*(1-((75-y)/75)^2) %m/s

    %Initial Conditions
    dt= 0.001 %s
    x(1)=0
    y(1)=50
    x2(1)=0
    y2(1)=50
    vx=U*cosd(theta)
    vy=U*sind(theta)
    vx2=U*cosd(theta)
    vy2=U*sind(theta)
    t(1)=0 
    t2(1)=0 
    %Start Loop
    i=1

    while min(y2)> -.001
        ay2=-g;
        ax2=0.0;
        vx2=vx2;
        vy2=vy2+ay2*dt;
        x2(i+1)=x2(i)+vx2*dt+.5*ax2*dt^2;
        y2(i+1)=y2(i)+vy2*dt+.5*ay2*dt^2;
        t2(i+1)=t2(i)+dt;
        i=i+1;
    end
    i=1
    while min(y)> -.001
        ax=-(D/m)*(vx*vx+vy*vy)^0.5*vx;
        ay=-g-(D/m)*(vx*vx+vy*vy)^0.5*vy;
        vx=vx+ax*dt;
        vy=vy+ay*dt;
        x(i+1)=x(i)+vx*dt+.5*ax*dt^2;
        y(i+1)=y(i)+vy*dt+.5*ay*dt^2;
        t(i+1)=t(i)+dt;
        i=i+1;
    end

      plot(x,y,'-',x2,y2,'-')
      legend('Drag', 'No Drag')
      legend('show')
      xlabel('x distance (m)')
      ylabel('y distance (m)')
      title('Projectile Path')

[madhan ravi]

maybe try

Uwind = @(y) -75*(1-((75-y)/75)^2)

for some reason I'm not able to run your code , takes long time

[John Rae]

It doesn't seem like its changing anything. When I add it into the vx components it doesn't alter the final plot

[madhan ravi]

It doesn't seem like its changing anything. When I add it into the vx components it doesn't alter the final plot

can you show the code?

[John Rae]

ax=-(D/m)*(vx*vx+vy*vy)^0.5*vx;

        ay=-g-(D/m)*(vx*vx+vy*vy)^0.5*vy;

        vx=Uwind+vx+ax*dt;

        vy=vy+ay*dt;

        x(i+1)=x(i)+vx*dt+.5*ax*dt^2;

        y(i+1)=y(i)+vy*dt+.5*ay*dt^2;

        t(i+1)=t(i)+dt;

        i=i+1;