Error using function fplot

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Garrett Crawford
Garrett Crawford 2020-5-11
评论： Ameer Hamza 2020-5-11
When typing my code, I keep getting the error of invalid parameter from fplot. Not sure why it keeps coming up. How would I fix this?
Code:
syms x
f(x) = log(x)^4 * exp((-x)^3) * x^2;
val = int(f(x),x,[0,Inf]);
vpa(val)
X = [0.5 : 0.1 : 2.5]
fplot(@(x) f(x),X,'b')
  1 个评论
Geoff Hayes
Geoff Hayes 2020-5-11
Garrett - what happens if you don't use a symbolic expression? From fplot 'f' input parameter, the first parameter is a function handle. Or, perhaps you can convert the f to a MATLAB function handle with matlabfunction.

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Ameer Hamza
Ameer Hamza 2020-5-11
编辑：Ameer Hamza 2020-5-11
You need to specify range with two numbers.
syms x
f(x) = log(x)^4 * exp((-x)^3) * x^2;
val = int(f(x),x,[0,Inf]);
fplot(@(x) f(x), [0.5 2.5],'b')
  2 个评论
Garrett Crawford
Garrett Crawford 2020-5-11
The problem is to write a script to evaluate the integral f(x) = log(x)^4 * exp((-x)^3) * x^2;from x=0 to x=Infinity but to Also, plot x versesf(x),for x =[.5 : .1 : 2.5]. Would ths solution stil corelate with what was asked in the problem?
Ameer Hamza
Ameer Hamza 2020-5-11
I think the above solution with fplot() should be acceptable in this case. But if you still want to plot at these specific x-values then you can use plot() instead of fplot. However, as you can see, the graph is not as smooth
syms x
f(x) = log(x)^4 * exp((-x)^3) * x^2;
val = int(f(x),x,[0,Inf]);
X = 0.5:0.1:2.5;
plot(X, f(X), 'b')

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