Few activation functions handling various problems - neural networks












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How can a few activation functions in neural networks handle so many different problems?



I know some basics theory behind ANN, but I can't get what functions like the sigmoid function etc. have in common with for example image classification?










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    1












    $begingroup$


    How can a few activation functions in neural networks handle so many different problems?



    I know some basics theory behind ANN, but I can't get what functions like the sigmoid function etc. have in common with for example image classification?










    share|improve this question











    $endgroup$




    bumped to the homepage by Community 22 hours ago


    This question has answers that may be good or bad; the system has marked it active so that they can be reviewed.


















      1












      1








      1


      1



      $begingroup$


      How can a few activation functions in neural networks handle so many different problems?



      I know some basics theory behind ANN, but I can't get what functions like the sigmoid function etc. have in common with for example image classification?










      share|improve this question











      $endgroup$




      How can a few activation functions in neural networks handle so many different problems?



      I know some basics theory behind ANN, but I can't get what functions like the sigmoid function etc. have in common with for example image classification?







      neural-network deep-learning activation-function






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      edited Aug 8 '18 at 17:31









      oW_

      3,306933




      3,306933










      asked Aug 8 '18 at 15:44









      mikinoqwertmikinoqwert

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      bumped to the homepage by Community 22 hours ago


      This question has answers that may be good or bad; the system has marked it active so that they can be reviewed.
























          2 Answers
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          $begingroup$

          Image classification and other task can be expressed as function approximations and, in theory, neural networks can approximate (almost) any function (given few assumptions on the activation function (see Universal Approx. Theorem)).



          However, in practice, not all functions fulfilling these assumptions work equally well. Popular activation functions usually share some properties that allow neural networks to learn efficiently in practice, e.g. they are continuously differentiable (for gradient descent), close to the identity near zero (accelerates initial learning from small random weights) and so on.



          Activation functions like the sigmoid function are not directly related to image classification or any other tasks. Rather, they allow for efficient training of neural networks, which, in turn, can represent a wide variety of tasks using different architectures and cost functions.






          share|improve this answer









          $endgroup$













          • $begingroup$
            But I still don't get what in common have any function connected with some real-life-problems to tanh, sigmoid etc. And why do we use that kind of funcs, but not sin/cos. I know it is stupid question ,but I don't get it.
            $endgroup$
            – mikinoqwert
            Aug 8 '18 at 17:35












          • $begingroup$
            Not sure I understand 100%. Are you asking (a) what tanh, sigmoid, relu etc. have in common or (b) how sigmoid is related to say image classification? (a) they all allow efficient training of neural networks (cos/sin do not), (b) there is no relationship other than (a). Maybe you can rephrase your questions with a more detailed example?
            $endgroup$
            – oW_
            Aug 8 '18 at 17:42










          • $begingroup$
            I meant, why we use (for any task) sigmoid/tanh/etc. instead of cos/sin.
            $endgroup$
            – mikinoqwert
            Aug 8 '18 at 17:46



















          0












          $begingroup$

          To respond to your additional question of why sigmoid or tanh instead of sin or cos, I would say that while all of these functions are bounded in their output, only sigmoid and tanh are one to one functions.






          share|improve this answer









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            2 Answers
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            2 Answers
            2






            active

            oldest

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            active

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            active

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            0












            $begingroup$

            Image classification and other task can be expressed as function approximations and, in theory, neural networks can approximate (almost) any function (given few assumptions on the activation function (see Universal Approx. Theorem)).



            However, in practice, not all functions fulfilling these assumptions work equally well. Popular activation functions usually share some properties that allow neural networks to learn efficiently in practice, e.g. they are continuously differentiable (for gradient descent), close to the identity near zero (accelerates initial learning from small random weights) and so on.



            Activation functions like the sigmoid function are not directly related to image classification or any other tasks. Rather, they allow for efficient training of neural networks, which, in turn, can represent a wide variety of tasks using different architectures and cost functions.






            share|improve this answer









            $endgroup$













            • $begingroup$
              But I still don't get what in common have any function connected with some real-life-problems to tanh, sigmoid etc. And why do we use that kind of funcs, but not sin/cos. I know it is stupid question ,but I don't get it.
              $endgroup$
              – mikinoqwert
              Aug 8 '18 at 17:35












            • $begingroup$
              Not sure I understand 100%. Are you asking (a) what tanh, sigmoid, relu etc. have in common or (b) how sigmoid is related to say image classification? (a) they all allow efficient training of neural networks (cos/sin do not), (b) there is no relationship other than (a). Maybe you can rephrase your questions with a more detailed example?
              $endgroup$
              – oW_
              Aug 8 '18 at 17:42










            • $begingroup$
              I meant, why we use (for any task) sigmoid/tanh/etc. instead of cos/sin.
              $endgroup$
              – mikinoqwert
              Aug 8 '18 at 17:46
















            0












            $begingroup$

            Image classification and other task can be expressed as function approximations and, in theory, neural networks can approximate (almost) any function (given few assumptions on the activation function (see Universal Approx. Theorem)).



            However, in practice, not all functions fulfilling these assumptions work equally well. Popular activation functions usually share some properties that allow neural networks to learn efficiently in practice, e.g. they are continuously differentiable (for gradient descent), close to the identity near zero (accelerates initial learning from small random weights) and so on.



            Activation functions like the sigmoid function are not directly related to image classification or any other tasks. Rather, they allow for efficient training of neural networks, which, in turn, can represent a wide variety of tasks using different architectures and cost functions.






            share|improve this answer









            $endgroup$













            • $begingroup$
              But I still don't get what in common have any function connected with some real-life-problems to tanh, sigmoid etc. And why do we use that kind of funcs, but not sin/cos. I know it is stupid question ,but I don't get it.
              $endgroup$
              – mikinoqwert
              Aug 8 '18 at 17:35












            • $begingroup$
              Not sure I understand 100%. Are you asking (a) what tanh, sigmoid, relu etc. have in common or (b) how sigmoid is related to say image classification? (a) they all allow efficient training of neural networks (cos/sin do not), (b) there is no relationship other than (a). Maybe you can rephrase your questions with a more detailed example?
              $endgroup$
              – oW_
              Aug 8 '18 at 17:42










            • $begingroup$
              I meant, why we use (for any task) sigmoid/tanh/etc. instead of cos/sin.
              $endgroup$
              – mikinoqwert
              Aug 8 '18 at 17:46














            0












            0








            0





            $begingroup$

            Image classification and other task can be expressed as function approximations and, in theory, neural networks can approximate (almost) any function (given few assumptions on the activation function (see Universal Approx. Theorem)).



            However, in practice, not all functions fulfilling these assumptions work equally well. Popular activation functions usually share some properties that allow neural networks to learn efficiently in practice, e.g. they are continuously differentiable (for gradient descent), close to the identity near zero (accelerates initial learning from small random weights) and so on.



            Activation functions like the sigmoid function are not directly related to image classification or any other tasks. Rather, they allow for efficient training of neural networks, which, in turn, can represent a wide variety of tasks using different architectures and cost functions.






            share|improve this answer









            $endgroup$



            Image classification and other task can be expressed as function approximations and, in theory, neural networks can approximate (almost) any function (given few assumptions on the activation function (see Universal Approx. Theorem)).



            However, in practice, not all functions fulfilling these assumptions work equally well. Popular activation functions usually share some properties that allow neural networks to learn efficiently in practice, e.g. they are continuously differentiable (for gradient descent), close to the identity near zero (accelerates initial learning from small random weights) and so on.



            Activation functions like the sigmoid function are not directly related to image classification or any other tasks. Rather, they allow for efficient training of neural networks, which, in turn, can represent a wide variety of tasks using different architectures and cost functions.







            share|improve this answer












            share|improve this answer



            share|improve this answer










            answered Aug 8 '18 at 17:29









            oW_oW_

            3,306933




            3,306933












            • $begingroup$
              But I still don't get what in common have any function connected with some real-life-problems to tanh, sigmoid etc. And why do we use that kind of funcs, but not sin/cos. I know it is stupid question ,but I don't get it.
              $endgroup$
              – mikinoqwert
              Aug 8 '18 at 17:35












            • $begingroup$
              Not sure I understand 100%. Are you asking (a) what tanh, sigmoid, relu etc. have in common or (b) how sigmoid is related to say image classification? (a) they all allow efficient training of neural networks (cos/sin do not), (b) there is no relationship other than (a). Maybe you can rephrase your questions with a more detailed example?
              $endgroup$
              – oW_
              Aug 8 '18 at 17:42










            • $begingroup$
              I meant, why we use (for any task) sigmoid/tanh/etc. instead of cos/sin.
              $endgroup$
              – mikinoqwert
              Aug 8 '18 at 17:46


















            • $begingroup$
              But I still don't get what in common have any function connected with some real-life-problems to tanh, sigmoid etc. And why do we use that kind of funcs, but not sin/cos. I know it is stupid question ,but I don't get it.
              $endgroup$
              – mikinoqwert
              Aug 8 '18 at 17:35












            • $begingroup$
              Not sure I understand 100%. Are you asking (a) what tanh, sigmoid, relu etc. have in common or (b) how sigmoid is related to say image classification? (a) they all allow efficient training of neural networks (cos/sin do not), (b) there is no relationship other than (a). Maybe you can rephrase your questions with a more detailed example?
              $endgroup$
              – oW_
              Aug 8 '18 at 17:42










            • $begingroup$
              I meant, why we use (for any task) sigmoid/tanh/etc. instead of cos/sin.
              $endgroup$
              – mikinoqwert
              Aug 8 '18 at 17:46
















            $begingroup$
            But I still don't get what in common have any function connected with some real-life-problems to tanh, sigmoid etc. And why do we use that kind of funcs, but not sin/cos. I know it is stupid question ,but I don't get it.
            $endgroup$
            – mikinoqwert
            Aug 8 '18 at 17:35






            $begingroup$
            But I still don't get what in common have any function connected with some real-life-problems to tanh, sigmoid etc. And why do we use that kind of funcs, but not sin/cos. I know it is stupid question ,but I don't get it.
            $endgroup$
            – mikinoqwert
            Aug 8 '18 at 17:35














            $begingroup$
            Not sure I understand 100%. Are you asking (a) what tanh, sigmoid, relu etc. have in common or (b) how sigmoid is related to say image classification? (a) they all allow efficient training of neural networks (cos/sin do not), (b) there is no relationship other than (a). Maybe you can rephrase your questions with a more detailed example?
            $endgroup$
            – oW_
            Aug 8 '18 at 17:42




            $begingroup$
            Not sure I understand 100%. Are you asking (a) what tanh, sigmoid, relu etc. have in common or (b) how sigmoid is related to say image classification? (a) they all allow efficient training of neural networks (cos/sin do not), (b) there is no relationship other than (a). Maybe you can rephrase your questions with a more detailed example?
            $endgroup$
            – oW_
            Aug 8 '18 at 17:42












            $begingroup$
            I meant, why we use (for any task) sigmoid/tanh/etc. instead of cos/sin.
            $endgroup$
            – mikinoqwert
            Aug 8 '18 at 17:46




            $begingroup$
            I meant, why we use (for any task) sigmoid/tanh/etc. instead of cos/sin.
            $endgroup$
            – mikinoqwert
            Aug 8 '18 at 17:46











            0












            $begingroup$

            To respond to your additional question of why sigmoid or tanh instead of sin or cos, I would say that while all of these functions are bounded in their output, only sigmoid and tanh are one to one functions.






            share|improve this answer









            $endgroup$


















              0












              $begingroup$

              To respond to your additional question of why sigmoid or tanh instead of sin or cos, I would say that while all of these functions are bounded in their output, only sigmoid and tanh are one to one functions.






              share|improve this answer









              $endgroup$
















                0












                0








                0





                $begingroup$

                To respond to your additional question of why sigmoid or tanh instead of sin or cos, I would say that while all of these functions are bounded in their output, only sigmoid and tanh are one to one functions.






                share|improve this answer









                $endgroup$



                To respond to your additional question of why sigmoid or tanh instead of sin or cos, I would say that while all of these functions are bounded in their output, only sigmoid and tanh are one to one functions.







                share|improve this answer












                share|improve this answer



                share|improve this answer










                answered Aug 9 '18 at 2:01









                RossDeVitoRossDeVito

                1015




                1015






























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