how to solve undefined variable?

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SHARAD KUMAR UPADHYAY
回答： Walter Roberson 2019-8-6
% I am trying to do integration with the limit x<5, as
a=any const no, for eg a= 2
f=@(x) a*x^2+sin(pi*x/2)
if x>5
output=0
else
output=integral(f,0,inf,'ArrayValued',true,'RelTol',1e-4,'AbsTol',1e-4
end
%% but error I found---- Undefined function or variable 'x'. ,if x > 5
%% please solve it
  1 个评论
KSSV
KSSV 2019-8-5
f=@(x) a*x^2+sin(pi*x/2)
output=integral(f,0,inf,'ArrayValued',true,'RelTol',1e-4,'AbsTol',1e-4)

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回答（1 个）

Walter Roberson
Walter Roberson 2019-8-6
a=any const no, for eg a= 2
end
f=@(x) (x<5) .* (a*x^2+sin(pi*x/2));
output = integral(f,0,inf,'ArrayValued',true,'RelTol',1e-4,'AbsTol',1e-4)
Note: this might not give the right answer if f happens to be evaluated at +/- inf : there is a danger that it could return nan instead of the correct solution.

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