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

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Lewis
Lewis 2021-11-11
评论： the cyclist 2021-11-11
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

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采纳的回答

the cyclist
the cyclist 2021-11-11
编辑：the cyclist 2021-11-11
Ran in:
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.

更多回答（2 个）

Sulaymon Eshkabilov
Sulaymon Eshkabilov 2021-11-11
Ran in:
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
Sulaymon Eshkabilov
Sulaymon Eshkabilov 2021-11-11
Ran in:
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
the cyclist
the cyclist 2021-11-11
I like the legend idea. In this particular case, I would use
'location','southeast'
rather than 'best'.

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