Plotting simple functions bounded by inequalities

Hi,

I am trying to plot the albedo-ice feedback for a simple function as seen in the picture below:

This is the code I have written so far (where Ts_ is the temperature I have from an ODE previously solved where I had assumed alpha was constant):

m=-0.08;
j=linspace(min(Ts_),max(Ts_),100);
if j<-10
    alpha_variable=0.7
    if j>10
        alpha_variable=0.3
    else
        alpha_variable=m*j;
    end
end
figure(3);
plot(j,alpha_variable)

I am only plotting it to see that I have the correct relationship before moving on but for some reason the plot is just coming up as the linear equation at the bottom (i.e. alpha_variable=m*j).

I have tried changing j for Ts_ in my if statements, but this isn't working either.

Any help is much appreciated! :)

Thanks,

Emilia

Answer 1

[KSSV]

m=-0.08;
j=linspace(min(Ts_),max(Ts_),100);
alpha_variable = m*j ; 
alpha_variable(j<-10) = 0.7 ; 
alpha_variable(j>10) = 0.3 ; 

plot(j,alpha_variable)

[Emilia Miller]

Thank you! But now it is doing this, which is also not quite right...do you have any ideas?

[Torsten]

m=-(0.7-0.3)/(10-(-10));
j=linspace(-30,30,100);
alpha_variable = m*j+0.5 ; 
alpha_variable(j<-10) = 0.7 ; 
alpha_variable(j>10) = 0.3 ; 

plot(j,alpha_variable)

[Steven Lord]

1) The region where your function is not constant is between -10 and +10, but you're plotting this function over the interval (roughly) -275 to 20 or 30. If you changed the axes limits to exclude the region between -300 and say -20 your function will look a little different.

m=-0.08;
j=linspace(-20, 20,100);
alpha_variable = m*j ; 
alpha_variable(j<-10) = 0.7 ; 
alpha_variable(j>10) = 0.3 ; 

plot(j,alpha_variable)

2) You need to adjust the equation of the line you're using to connect the regions less than -10 (which has a constant value of 0.7) and the region greater than 10 (which has a constant value of 0.3.)

[Emilia Miller]

Ah thank you everybody!