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

 采纳的回答

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

更多回答(2 个)

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
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

1 个评论

I like the legend idea. In this particular case, I would use
'location','southeast'
rather than 'best'.

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