Can I use integral with symbolic/variable interval values?
29 views (last 30 days)
Show older comments
Brede Løvik Lillehammer
on 20 Jan 2014
Commented: giorgio vanni
on 24 Jan 2019
Hi. I'm wondering if it is possible to use, in some way, variable or symbolic interval values for the integral function. I need to solve a similar kind of problem shown below, can't think of a way to do it (my functions are quite huge, so it's not easy to somehow simplify it).
- Function 1: f(s)=...
- Function 2: g(x)=...
- f_new = integral(@(s) f, 0, x)
Now, both f_new and g is a function of x.
- Final function = integral(@(x) f_new*g, 0, 2)
Hope the question is somewhat clear. If not, just ask. Any help is appreciated! :)
0 Comments
Accepted Answer
Walter Roberson
on 20 Jan 2014
Assuming that f is a function handle already, such as
f = @(s) tan(s^2 + exp(-s));
then
f_new = @(x) integral(f, 0, x);
final_function = @(b) integral( @(x) f_new(x) .* g(x), 0, b);
and
final_function(2)
2 Comments
Mike Hosea
on 20 Jan 2014
You will need to vectorize f_new with arrayfun, e.g.
f_new = @(v)arrayfun(@(x)integral(f,0,x),v)
or, alternatively, prevent the outer integral from passing in non-scalars with the 'ArrayValued' option:
final_function = @(b)integral(@(x)f_new(x).*g(x), 0, b,'ArrayValued',true);
giorgio vanni
on 24 Jan 2019
I've copied the answer from Walter in an easier version, as follows:
fun=@(y)integral(@(x)x,0,y)
integral(fun,0,1)
But what I've obtained is the following:
Error using integral (line 85)
A and B must be floating-point scalars.
Error in @(y)integral(@(x)x,0,y)
Error in integralCalc/iterateScalarValued (line 314)
fx = FUN(t);
Error in integralCalc/vadapt (line 132)
[q,errbnd] = iterateScalarValued(u,tinterval,pathlen);
Error in integralCalc (line 75)
[q,errbnd] = vadapt(@AtoBInvTransform,interval);
Error in integral (line 88)
Q = integralCalc(fun,a,b,opstruct);
I can't understand where is the problem, can you help me?
More Answers (1)
Brede Løvik Lillehammer
on 21 Jan 2014
1 Comment
Walter Roberson
on 21 Jan 2014
int() is for symbolic integration. integral() is for numeric integration.
See Also
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!