My graph won't plot

f=@(x)((3+sin(2.*x))/(1+exp(0.03.*x.^2)))-1.2;
x=linspace(-6,6);
plot(x,f(x))
axis([-6 6 -1 1])

This is the code I've put in MATLAB. When i run the script an empty figure shows up without the graph. How can i fix it to show the graph in the figure?

Answer 1

[Cris LaPierre]

The issue is that you are performing a matrix division in your function, which results in a single value. It looks like you want element-wise. Use "./" instead. See here for more details.

f=@(x)((3+sin(2.*x))./(1+exp(0.03.*x.^2)))-1.2;
%                   ^^
x=linspace(-6,6);
plot(x,f(x))
axis([-6 6 -1 1])

Answer 2

[Voss]

Your expression for f contains matrix division (/), which causes f(x) to return a scalar, so the vectors you're plotting (x and f(x)) have different lengths, which is why the plot is empty. To fix it, change the matrix division to element-wise division (./), like this:

f=@(x)((3+sin(2.*x))./(1+exp(0.03.*x.^2)))-1.2;

[Wilma Sunnerberg]

Okay, thank you so much for the help!

[Cris LaPierre]

Just one clarification. When plotting with a vector for x and a scalar for y, MATLAB reuses the same y value for each x value. The reason nothing appears is because each value is plotted as a separate data series of a single point. The default plot format is a solid line without a marker, so nothing is visible for a single point. If you include a marker style in your plot syntax, you will see what is happening.

f=@(x)((3+sin(2.*x))/(1+exp(0.03.*x.^2)))-1.2;
x=linspace(-6,6);
plot(x,f(x),'-o')
%             ^
axis([-6 6 -1 1])