How to get rid of the straight line?

[kim1]

Hi guys this may sound weird but Im trying to plot my graph without the straight line that connecting to the curve in it, unfortunately I dont know how from my own equation. so that the result at the end i will get a smooth curve.

Molar_mass=27
P0=15
P0_pa=1519875
p_amb=101325
R=8314
Rspec=R/Molar_mass
Cp=2112
Cv=Cp-Rspec
γ=Cp/Cv
Pe=0.372
Thrust_exit=450000
T0=2500
Te=(Pe/P0)^((γ-1)/γ)*T0
T_Throat=T0*(2/(γ+1))
Me=sqrt((2/(γ-1))*((P0/Pe)^((γ-1)/γ)-1))
Ae=sqrt(γ*Rspec*Te)
Ue=Me*Ae
ṁ=Thrust_exit/Ue
ρ0=(Molar_mass*P0_pa)/(R*T0)
ρ_Throat=ρ0*(2/(γ+1))^(γ/(γ-1))
A_star=ṁ/(ρ0*((2/(γ+1))^(1/(γ-1)))*sqrt(γ*Rspec*(2/(γ+1))*T0))
A_ratio=A_star*sqrt((1/Me^2)*((2/(γ+1))*(1+((γ-1)/2)*(Me^2)))^((γ+1)/(γ-1)))
a_star=sqrt(γ*Rspec*T0*(2/(γ+1)))

θ=30*pi/180
R_throat=sqrt(A_star/pi)
R1=1.5*R_throat
ϵ=A_ratio/A_star
R0=sqrt(ϵ)*R_throat
Rm=R_throat+R1*(1-cos(θ))
λ=(1+cos(θ))/2 
Lm=(R0-R_throat+R1*(cos(θ)-1))/tan(θ)
Lcc=(R_throat*(sqrt(ϵ)-1)+R1*(cos(θ)-1))/tan(θ)+(R1*sin(θ))
L2=Lcc-Lm
Xm=R1*sin(θ)
Ym=R_throat+R1*(1-cos(θ))
X_inlet=Xm+Lm
Y_inlet=R0+R1*(1-cos(θ))
m=(Y_inlet-Ym)/(X_inlet-Xm)
Y02=Ym

using Plots

function f(x; θ=30pi/180)
    
    global Y02, R1, R_throat, m

    if -R1*sin(θ) < x < R1*sin(θ)

        return R_throat + R1 * (1 - cos(asin(x/R1)))

    else
        return Y02

    end
end

x2 = range(0, X_inlet, length=50)
plot(-x2, f.(x2), color=:blue, label=missing)
plot!(-x2, -f.(x2), color=:blue, label=missing)
plot!(ylims=(-0.75,0.75))

[Christopher_Fisher]

If the values on the line are equal, and occur in the same place in the vectors, it would be easy to do something like keep_idx = y_line .!= y, where y_line is the value associated with the line, and y = f.(x2). You can use keep_idx to filter out the line.

[kim1]

The line is still there eventhough i put the keep_idx , what could i had done wrong

x2 = range(0, X_inlet, length=50)
y=f.(x2)
keep_idx=Y02 .!=y
plot(-x2, f.(x2), color=:blue, label=missing)
plot!(-x2, -f.(x2), color=:blue, label=missing)
plot!(ylims=(-0.75,0.75))

[Christopher_Fisher]

You still need to use keep_idx remove elements from x2 and y. Each element in keep_idx is a boolean, which will keep a value if true and will exclude a value if false. So what you need to do is index x2 and y like so:

x2 = range(0, X_inlet, length=50)
y=f.(x2)
keep_idx=Y02 .!=y
plot(-x2[keep_idx], y[keep_idx], color=:blue, label=missing)
plot!(-x2[keep_idx], -y[keep_idx], color=:blue, label=missing)
plot!(ylims=(-0.75,0.75))

[kim1]

I have try and put in your code its turns out like this.

[JM_Beckers]

You code does not provide the values of A_star and A_ratio, which makes it difficult for testing your code (Please read: make it easier to help you)

[kim1]

sorry just edited my post

[JM_Beckers]

Now Molar_mass is not defined. Please check before posting that a MWE is actually working, you will get much quicker help.

[kim1]

just edited it forgot to copy the molar mass.

[JM_Beckers]

This is what I get with your code and which does not correspond to your first plot, so you probably changed some values

Anyway, when I apply the solution How to get rid of the straight line? - #4 by Christopher_Fisher

x2 = range(0, X_inlet, length=50)
y=f.(x2)
keep_idx=Y02 .!=y
plot(-x2[keep_idx], y[keep_idx], color=:blue, label=missing)
plot!(-x2[keep_idx], -y[keep_idx], color=:blue, label=missing)
plot!(ylims=(-0.75,0.75))

it does exactly what you asked for, taking away the constant line.

[kim1]

I meant like just deleting the whole line so will get a graph look like this

Because then i got to figure out how to do the next curve replacing the straigh line

[JM_Beckers]

Still not sure what you actually ask. If it is just a graphic windows problem, either add your next curve with plot! and the axes will adapt or force the axes with plot!(xlims=(-.7,0)) for example.