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Convolutions of two functions


Define uniform B-spline basis functions via continuous convolutionHow Heaviside step function changes limits of integrationHow to obtain the convolution directly (not graphical) of the two functions $e^{-t}u(t)$ and $e^{-2t}u(t)$?Convolution of Two Shifted FunctionsConvolution integral involving two Heaviside functionsConvolution Integral - Shift propertyQuestion on the uniqueness of the densitiesprobability of two numbers picked from two distributions giving a fixed number multiplicationDifficult convolutions in probability problemsExample of non-zero functions with identically zero convolution













0












$begingroup$


I am having trouble understanding how you take the convolution of two functions.



For example, if $f_1(x) = x$, with x ranging from [0,X] how do I solve for $f_2(x)$ when
$$f_2(x) = int_{0}^{infty} f_1(x')f_1(x-x') dx'.$$
Do I need to use an indicator function?



Thanks










share|cite|improve this question











$endgroup$








  • 1




    $begingroup$
    This integral does not converge for your choice of $f_1$.
    $endgroup$
    – Mars Plastic
    Mar 13 at 16:22










  • $begingroup$
    Also: I suppose $*$ denotes multiplication and not convolution?
    $endgroup$
    – Mars Plastic
    Mar 13 at 17:01










  • $begingroup$
    yes you are correct
    $endgroup$
    – Calvin Xu
    Mar 14 at 17:03
















0












$begingroup$


I am having trouble understanding how you take the convolution of two functions.



For example, if $f_1(x) = x$, with x ranging from [0,X] how do I solve for $f_2(x)$ when
$$f_2(x) = int_{0}^{infty} f_1(x')f_1(x-x') dx'.$$
Do I need to use an indicator function?



Thanks










share|cite|improve this question











$endgroup$








  • 1




    $begingroup$
    This integral does not converge for your choice of $f_1$.
    $endgroup$
    – Mars Plastic
    Mar 13 at 16:22










  • $begingroup$
    Also: I suppose $*$ denotes multiplication and not convolution?
    $endgroup$
    – Mars Plastic
    Mar 13 at 17:01










  • $begingroup$
    yes you are correct
    $endgroup$
    – Calvin Xu
    Mar 14 at 17:03














0












0








0





$begingroup$


I am having trouble understanding how you take the convolution of two functions.



For example, if $f_1(x) = x$, with x ranging from [0,X] how do I solve for $f_2(x)$ when
$$f_2(x) = int_{0}^{infty} f_1(x')f_1(x-x') dx'.$$
Do I need to use an indicator function?



Thanks










share|cite|improve this question











$endgroup$




I am having trouble understanding how you take the convolution of two functions.



For example, if $f_1(x) = x$, with x ranging from [0,X] how do I solve for $f_2(x)$ when
$$f_2(x) = int_{0}^{infty} f_1(x')f_1(x-x') dx'.$$
Do I need to use an indicator function?



Thanks







integration probability-distributions convolution






share|cite|improve this question















share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited Mar 14 at 17:02







Calvin Xu

















asked Mar 13 at 16:15









Calvin XuCalvin Xu

11




11








  • 1




    $begingroup$
    This integral does not converge for your choice of $f_1$.
    $endgroup$
    – Mars Plastic
    Mar 13 at 16:22










  • $begingroup$
    Also: I suppose $*$ denotes multiplication and not convolution?
    $endgroup$
    – Mars Plastic
    Mar 13 at 17:01










  • $begingroup$
    yes you are correct
    $endgroup$
    – Calvin Xu
    Mar 14 at 17:03














  • 1




    $begingroup$
    This integral does not converge for your choice of $f_1$.
    $endgroup$
    – Mars Plastic
    Mar 13 at 16:22










  • $begingroup$
    Also: I suppose $*$ denotes multiplication and not convolution?
    $endgroup$
    – Mars Plastic
    Mar 13 at 17:01










  • $begingroup$
    yes you are correct
    $endgroup$
    – Calvin Xu
    Mar 14 at 17:03








1




1




$begingroup$
This integral does not converge for your choice of $f_1$.
$endgroup$
– Mars Plastic
Mar 13 at 16:22




$begingroup$
This integral does not converge for your choice of $f_1$.
$endgroup$
– Mars Plastic
Mar 13 at 16:22












$begingroup$
Also: I suppose $*$ denotes multiplication and not convolution?
$endgroup$
– Mars Plastic
Mar 13 at 17:01




$begingroup$
Also: I suppose $*$ denotes multiplication and not convolution?
$endgroup$
– Mars Plastic
Mar 13 at 17:01












$begingroup$
yes you are correct
$endgroup$
– Calvin Xu
Mar 14 at 17:03




$begingroup$
yes you are correct
$endgroup$
– Calvin Xu
Mar 14 at 17:03










1 Answer
1






active

oldest

votes


















1












$begingroup$

in your example you sustitute $f_1(x')=x'$ and $f_1(x-x')=x-x'$ in an analagous way and solve the integral having the $x'$ as your integral's variable.



If the integral converges, you will get a result in terms of x and it will be the convolution of $f_1$ with itself. if the integral dows not converge, you can't make the convolution.






share|cite|improve this answer









$endgroup$













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    1 Answer
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    1 Answer
    1






    active

    oldest

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    active

    oldest

    votes






    active

    oldest

    votes









    1












    $begingroup$

    in your example you sustitute $f_1(x')=x'$ and $f_1(x-x')=x-x'$ in an analagous way and solve the integral having the $x'$ as your integral's variable.



    If the integral converges, you will get a result in terms of x and it will be the convolution of $f_1$ with itself. if the integral dows not converge, you can't make the convolution.






    share|cite|improve this answer









    $endgroup$


















      1












      $begingroup$

      in your example you sustitute $f_1(x')=x'$ and $f_1(x-x')=x-x'$ in an analagous way and solve the integral having the $x'$ as your integral's variable.



      If the integral converges, you will get a result in terms of x and it will be the convolution of $f_1$ with itself. if the integral dows not converge, you can't make the convolution.






      share|cite|improve this answer









      $endgroup$
















        1












        1








        1





        $begingroup$

        in your example you sustitute $f_1(x')=x'$ and $f_1(x-x')=x-x'$ in an analagous way and solve the integral having the $x'$ as your integral's variable.



        If the integral converges, you will get a result in terms of x and it will be the convolution of $f_1$ with itself. if the integral dows not converge, you can't make the convolution.






        share|cite|improve this answer









        $endgroup$



        in your example you sustitute $f_1(x')=x'$ and $f_1(x-x')=x-x'$ in an analagous way and solve the integral having the $x'$ as your integral's variable.



        If the integral converges, you will get a result in terms of x and it will be the convolution of $f_1$ with itself. if the integral dows not converge, you can't make the convolution.







        share|cite|improve this answer












        share|cite|improve this answer



        share|cite|improve this answer










        answered Mar 13 at 17:07









        Carlos Adrian Perez EstradaCarlos Adrian Perez Estrada

        414




        414






























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