Is there any error in my code?

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LAWRENCE DUMEBI
LAWRENCE DUMEBI 2017-6-9
编辑： John BG 2017-6-11
These are my codes to plot the graph of f(x, q) = (q^4/(q^3+6))(1+x^3)exp(-qx)
clear all
q = 0.4;
x = linspace(0,20);
for i = 1:length(x);
f(i) = (q^4/(q^3+6))*(1+x(i))*exp(-q*x(i));
end
plot(x,f,'linewidth',2)
xlabel(x)
ylabel('f(x)')
please reply me with the correction. Thanks.
  2 个评论
Adam
Adam 2017-6-9
编辑：Adam 2017-6-9
You are missing a ^3 from your code, but this really is something you should double-check yourself before asking other people!
You don't need a for loop either, you can just vectorise it, but if at the moment you are only at the level of for loops I will leave that aside.
You can also easily create a quick test script with correct results calculated by hand or by calculator to check whether your answer is right or not.
Jan
Jan 2017-6-9
I've used the "{} Code" button to format your code, which was unreadable. Please do this by your own in the future - thanks.

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采纳的回答

John BG
John BG 2017-6-11
编辑：John BG 2017-6-11
Hi Lawrence
this is John BG ( <mailto:jgb2012@sky.com jgb2012@sky.com> )
even better, since you are after f(x,q) perhaps a 2D plot is more helpful
q = [0:.1:4];
x = linspace(0,20);
[Q,X]=meshgrid(q,x)
F = (Q.^4 ./ (Q.^3 + 6)) .* (1 + X.^3) .* exp(-Q .* X);
surf(F)
.
.
So Lawrence, if you find this answer useful would you please be so kind to consider marking my answer as Accepted Answer?
To any other reader, if you find this answer useful please consider clicking on the thumbs-up vote link
thanks in advance
John BG
<mailto:jgb2012@sky.com jgb2012@sky.com>

更多回答（1 个）

Jan
Jan 2017-6-9
编辑：Jan 2017-6-9
The ^3 in (1+x^3) has been forgotton:
... (1+x(i)^3) ...
You can do this without a loop also:
x = linspace(0,20);
f = (q^4 / (q^3 + 6)) * (1 + x.^3) .* exp(-q * x);

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