How to plot graph with multiple values of x in a function

This code should produce graphs for y=(x^3)-(4*(x^2))-x-4. My code is incorrect because it is raising the whole x matrix to powers in the plot() function rather than considering each element in the matrix. How do I solve this?

Thanks

count=0
for i=[3,5,7,10,20,100]
    count=count+1;
    x=linspace(-5,2,i)
    subplot(2,3,count)
    plot(x,(x^3)-(4*(x^2))-x-4,'-xr')
end

Answer 1

[the cyclist]

You need to use elementwise operations:

count=0;
for i=[3,5,7,10,20,100]
    count=count+1;
    x=linspace(-5,2,i);
    subplot(2,3,count)
    plot(x,(x.^3)-(4*(x.^2))-x-4,'-xr')
end

See Array vs. Matrix Operatoins.

Answer 2

[Sulaymon Eshkabilov]

A small (but crucial) err that is elementwise operation needed, e.g.:

count=0;
for i=[3,5,7,10,20,100]
    count=count+1;
    x=linspace(-5,2,i);
    subplot(2,3,count)
    plot(x,(x.^3)-(4*(x.^2))-x-4,'-xr')
end

Answer 3

[Sulaymon Eshkabilov]

You may also consider to display a legend showing the number of x values taken for calc and plot in every iteration:

count=0;
for i=[3,5,7,10,20,100]
    count=count+1;
    x=linspace(-5,2,i);
    subplot(2,3,count)
    plot(x,(x.^3)-(4*(x.^2))-x-4,'-xr')
    legend(['N_x = ', num2str(i)], 'location', 'best')
end

[the cyclist]

I like the legend idea. In this particular case, I would use

'location','southeast'

rather than 'best'.