fplot graph error getting y=0

Im creating a graph for a simple function, but instead im getting a line at y=0 plotted. My range needs to be [-4,8] but it seems that when I type negative numbers in my range is when this error occurs. If I make the range [0,8] the graph appears normal but as soon as i change it to even [-1,8] I get just a line at y=0.

Additionally, when I open the figure in a seperate figure window it shows the proper graph, but in the graph that actually appears in the live script it is still y=0. I have no idea why this is happening.

Here is my code:

math=@(x)0.6.*x.^3.*exp(-0.4./x)+1.5.*x.^2.*exp(-0.6.*x);

fplot(math,[-1,8])
xlabel('\bfx')
ylabel('\bfy')
title('y=0.6x^3e^{-0.4/x}+1.5x^2e^{-0.6x}')

%here is what I mean about it working for positive ranges
math=@(x)0.6.*x.^3.*exp(-0.4./x)+1.5.*x.^2.*exp(-0.6.*x);

fplot(math,[0,8])
xlabel('\bfx')
ylabel('\bfy')
title('y=0.6x^3e^{-0.4/x}+1.5x^2e^{-0.6x}')

Answer 1

[David Hill]

There is a sinularity around -5.6e-4 (advoid this area)

math=@(x)0.6.*x.^3.*exp(-0.4./x)+1.5.*x.^2.*exp(-0.6.*x);
fplot(math,[-4,-.01]);
hold on;
fplot(math,[0,8]);
xlabel('\bfx')
ylabel('\bfy')
title('y=0.6x^3e^{-0.4/x}+1.5x^2e^{-0.6x}')

[chelsea]

ah yes! thank you!