Is there a way to integrate the log of a function, f(x) in Matlab without defining eg l = log(f(x)?












3















I have the following code:



x = 0:0.001:2.5;

gamma_l = @(x) 2*x;


And I want to integrate the following:



integral( log(gamma_l), 0 , 0.6 )


But it gives me the error:




Undefined function 'log' for input arguments of type
'function_handle'.




I know that I could just define:



gamma_l_l = @(x) log(2*x);

integral( gamma_l_l, 0 , 0.6 )


Because it works in this way. However, I would like to know why the first case does not work. And if there is a way to integrate the function without defining a new function.






matlab integration







share|improve this question


















  • 1





    The first case does not work because log() requires numbers as inputs, and you are not giving it a number, you are giving it a function handle. The logarithm of a function handle is not defined.

    – Ander Biguri
    Nov 13 '18 at 16:07













  • Thanks, @Ander! So do you think that the most efficient (only) way is to define another function? Isn't there a way to define composite function inside the integral?

    – Tecon
    Nov 13 '18 at 16:11






  • 1





    Gnovice's answer is how you should handle this ;)

    – Ander Biguri
    Nov 13 '18 at 16:32
















3















I have the following code:



x = 0:0.001:2.5;

gamma_l = @(x) 2*x;


And I want to integrate the following:



integral( log(gamma_l), 0 , 0.6 )


But it gives me the error:




Undefined function 'log' for input arguments of type
'function_handle'.




I know that I could just define:



gamma_l_l = @(x) log(2*x);

integral( gamma_l_l, 0 , 0.6 )


Because it works in this way. However, I would like to know why the first case does not work. And if there is a way to integrate the function without defining a new function.






matlab integration







share|improve this question


















  • 1





    The first case does not work because log() requires numbers as inputs, and you are not giving it a number, you are giving it a function handle. The logarithm of a function handle is not defined.

    – Ander Biguri
    Nov 13 '18 at 16:07













  • Thanks, @Ander! So do you think that the most efficient (only) way is to define another function? Isn't there a way to define composite function inside the integral?

    – Tecon
    Nov 13 '18 at 16:11






  • 1





    Gnovice's answer is how you should handle this ;)

    – Ander Biguri
    Nov 13 '18 at 16:32














3












3








3








I have the following code:



x = 0:0.001:2.5;

gamma_l = @(x) 2*x;


And I want to integrate the following:



integral( log(gamma_l), 0 , 0.6 )


But it gives me the error:




Undefined function 'log' for input arguments of type
'function_handle'.




I know that I could just define:



gamma_l_l = @(x) log(2*x);

integral( gamma_l_l, 0 , 0.6 )


Because it works in this way. However, I would like to know why the first case does not work. And if there is a way to integrate the function without defining a new function.






matlab integration







share|improve this question














I have the following code:



x = 0:0.001:2.5;

gamma_l = @(x) 2*x;


And I want to integrate the following:



integral( log(gamma_l), 0 , 0.6 )


But it gives me the error:




Undefined function 'log' for input arguments of type
'function_handle'.




I know that I could just define:



gamma_l_l = @(x) log(2*x);

integral( gamma_l_l, 0 , 0.6 )


Because it works in this way. However, I would like to know why the first case does not work. And if there is a way to integrate the function without defining a new function.






matlab integration




matlab integration






share|improve this question













share|improve this question











share|improve this question




share|improve this question










asked Nov 13 '18 at 16:05









TeconTecon

183




183








  • 1





    The first case does not work because log() requires numbers as inputs, and you are not giving it a number, you are giving it a function handle. The logarithm of a function handle is not defined.

    – Ander Biguri
    Nov 13 '18 at 16:07













  • Thanks, @Ander! So do you think that the most efficient (only) way is to define another function? Isn't there a way to define composite function inside the integral?

    – Tecon
    Nov 13 '18 at 16:11






  • 1





    Gnovice's answer is how you should handle this ;)

    – Ander Biguri
    Nov 13 '18 at 16:32














  • 1





    The first case does not work because log() requires numbers as inputs, and you are not giving it a number, you are giving it a function handle. The logarithm of a function handle is not defined.

    – Ander Biguri
    Nov 13 '18 at 16:07













  • Thanks, @Ander! So do you think that the most efficient (only) way is to define another function? Isn't there a way to define composite function inside the integral?

    – Tecon
    Nov 13 '18 at 16:11






  • 1





    Gnovice's answer is how you should handle this ;)

    – Ander Biguri
    Nov 13 '18 at 16:32








1




1





The first case does not work because log() requires numbers as inputs, and you are not giving it a number, you are giving it a function handle. The logarithm of a function handle is not defined.

– Ander Biguri
Nov 13 '18 at 16:07







The first case does not work because log() requires numbers as inputs, and you are not giving it a number, you are giving it a function handle. The logarithm of a function handle is not defined.

– Ander Biguri
Nov 13 '18 at 16:07















Thanks, @Ander! So do you think that the most efficient (only) way is to define another function? Isn't there a way to define composite function inside the integral?

– Tecon
Nov 13 '18 at 16:11





Thanks, @Ander! So do you think that the most efficient (only) way is to define another function? Isn't there a way to define composite function inside the integral?

– Tecon
Nov 13 '18 at 16:11




1




1





Gnovice's answer is how you should handle this ;)

– Ander Biguri
Nov 13 '18 at 16:32





Gnovice's answer is how you should handle this ;)

– Ander Biguri
Nov 13 '18 at 16:32












1 Answer
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Your variable gamma_l is an anonymous function, and the log function is not designed to accept function handles as an input. Instead, you need to define a second anonymous function that evaluates gamma_l for a given value, then passes the numeric result to log, like so:



result = integral(@(x) log(gamma_l(x)), 0, 0.6);





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    1 Answer
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    1 Answer
    1






    active

    oldest

    votes









    active

    oldest

    votes






    active

    oldest

    votes









    5














    Your variable gamma_l is an anonymous function, and the log function is not designed to accept function handles as an input. Instead, you need to define a second anonymous function that evaluates gamma_l for a given value, then passes the numeric result to log, like so:



    result = integral(@(x) log(gamma_l(x)), 0, 0.6);





    share|improve this answer






























      5














      Your variable gamma_l is an anonymous function, and the log function is not designed to accept function handles as an input. Instead, you need to define a second anonymous function that evaluates gamma_l for a given value, then passes the numeric result to log, like so:



      result = integral(@(x) log(gamma_l(x)), 0, 0.6);





      share|improve this answer




























        5












        5








        5







        Your variable gamma_l is an anonymous function, and the log function is not designed to accept function handles as an input. Instead, you need to define a second anonymous function that evaluates gamma_l for a given value, then passes the numeric result to log, like so:



        result = integral(@(x) log(gamma_l(x)), 0, 0.6);





        share|improve this answer















        Your variable gamma_l is an anonymous function, and the log function is not designed to accept function handles as an input. Instead, you need to define a second anonymous function that evaluates gamma_l for a given value, then passes the numeric result to log, like so:



        result = integral(@(x) log(gamma_l(x)), 0, 0.6);






        share|improve this answer














        share|improve this answer



        share|improve this answer








        edited Nov 13 '18 at 16:14

























        answered Nov 13 '18 at 16:08









        gnovicegnovice

        116k13231335




        116k13231335






























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