Question about the proof that ${h_a: h_a(x) = 1 text{ if } x < a, a in Bbb R }$ is learnable.












1












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From Understanding Machine Learning :



My three questions about the proof in the below image are:




(1.) In the red box below, why is $(b_0, b_1)$ a valid interval?



(2.) How does $b_s$ being a threshold corresponding to an ERM hypothesis $h_S$ imply that $b_s in (b_0,
b_1)$
?



(3.) In the blue box, what makes this condition sufficient?




Assume $S={(x, y)}_{sampled}$ is some training set. Order all the $2$-tuples by their $x$ component and just write the $y$ values to get $S=(y_{x_0}, y_{x_1}, dots, y_{x_n}).$ As an example suppose we have $S=(1,0,1,0)$. Then we have $large S = (1, 0_{b_1}, 1_{b_0}, 0)$. But then we have improper interval notation.



What am I misunderstanding in the proof of this lemma?





enter image description here










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$endgroup$

















    1












    $begingroup$


    From Understanding Machine Learning :



    My three questions about the proof in the below image are:




    (1.) In the red box below, why is $(b_0, b_1)$ a valid interval?



    (2.) How does $b_s$ being a threshold corresponding to an ERM hypothesis $h_S$ imply that $b_s in (b_0,
    b_1)$
    ?



    (3.) In the blue box, what makes this condition sufficient?




    Assume $S={(x, y)}_{sampled}$ is some training set. Order all the $2$-tuples by their $x$ component and just write the $y$ values to get $S=(y_{x_0}, y_{x_1}, dots, y_{x_n}).$ As an example suppose we have $S=(1,0,1,0)$. Then we have $large S = (1, 0_{b_1}, 1_{b_0}, 0)$. But then we have improper interval notation.



    What am I misunderstanding in the proof of this lemma?





    enter image description here










    share|cite|improve this question











    $endgroup$















      1












      1








      1





      $begingroup$


      From Understanding Machine Learning :



      My three questions about the proof in the below image are:




      (1.) In the red box below, why is $(b_0, b_1)$ a valid interval?



      (2.) How does $b_s$ being a threshold corresponding to an ERM hypothesis $h_S$ imply that $b_s in (b_0,
      b_1)$
      ?



      (3.) In the blue box, what makes this condition sufficient?




      Assume $S={(x, y)}_{sampled}$ is some training set. Order all the $2$-tuples by their $x$ component and just write the $y$ values to get $S=(y_{x_0}, y_{x_1}, dots, y_{x_n}).$ As an example suppose we have $S=(1,0,1,0)$. Then we have $large S = (1, 0_{b_1}, 1_{b_0}, 0)$. But then we have improper interval notation.



      What am I misunderstanding in the proof of this lemma?





      enter image description here










      share|cite|improve this question











      $endgroup$




      From Understanding Machine Learning :



      My three questions about the proof in the below image are:




      (1.) In the red box below, why is $(b_0, b_1)$ a valid interval?



      (2.) How does $b_s$ being a threshold corresponding to an ERM hypothesis $h_S$ imply that $b_s in (b_0,
      b_1)$
      ?



      (3.) In the blue box, what makes this condition sufficient?




      Assume $S={(x, y)}_{sampled}$ is some training set. Order all the $2$-tuples by their $x$ component and just write the $y$ values to get $S=(y_{x_0}, y_{x_1}, dots, y_{x_n}).$ As an example suppose we have $S=(1,0,1,0)$. Then we have $large S = (1, 0_{b_1}, 1_{b_0}, 0)$. But then we have improper interval notation.



      What am I misunderstanding in the proof of this lemma?





      enter image description here







      probability proof-explanation machine-learning






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      edited Jan 15 at 16:01







      Oliver G

















      asked Jan 15 at 15:45









      Oliver GOliver G

      1,5791530




      1,5791530






















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          $begingroup$

          $S=(1,0,1,0)$ is not in the function class. If $h_a(x_1)=1$ and $h_a(x_2)=0$, then $x_1<x_2$. So $b_0$ is always smaller than $b_1$.






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            That answers $1$ and $2$. Do you have any idea about $3$? I can't see why those conditions are sufficient.
            $endgroup$
            – Oliver G
            Jan 16 at 15:34










          • $begingroup$
            Recall that at $a^*$ the loss is zero. If you move the threshold to $a_0$ or $a_1$, the loss will be $epsilon$. Take into account that the loss funtion is monotonous (in this case, not in general) and you see that it is sufficient
            $endgroup$
            – Micky Messer
            Jan 19 at 8:51











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          $begingroup$

          $S=(1,0,1,0)$ is not in the function class. If $h_a(x_1)=1$ and $h_a(x_2)=0$, then $x_1<x_2$. So $b_0$ is always smaller than $b_1$.






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            That answers $1$ and $2$. Do you have any idea about $3$? I can't see why those conditions are sufficient.
            $endgroup$
            – Oliver G
            Jan 16 at 15:34










          • $begingroup$
            Recall that at $a^*$ the loss is zero. If you move the threshold to $a_0$ or $a_1$, the loss will be $epsilon$. Take into account that the loss funtion is monotonous (in this case, not in general) and you see that it is sufficient
            $endgroup$
            – Micky Messer
            Jan 19 at 8:51
















          1












          $begingroup$

          $S=(1,0,1,0)$ is not in the function class. If $h_a(x_1)=1$ and $h_a(x_2)=0$, then $x_1<x_2$. So $b_0$ is always smaller than $b_1$.






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            That answers $1$ and $2$. Do you have any idea about $3$? I can't see why those conditions are sufficient.
            $endgroup$
            – Oliver G
            Jan 16 at 15:34










          • $begingroup$
            Recall that at $a^*$ the loss is zero. If you move the threshold to $a_0$ or $a_1$, the loss will be $epsilon$. Take into account that the loss funtion is monotonous (in this case, not in general) and you see that it is sufficient
            $endgroup$
            – Micky Messer
            Jan 19 at 8:51














          1












          1








          1





          $begingroup$

          $S=(1,0,1,0)$ is not in the function class. If $h_a(x_1)=1$ and $h_a(x_2)=0$, then $x_1<x_2$. So $b_0$ is always smaller than $b_1$.






          share|cite|improve this answer









          $endgroup$



          $S=(1,0,1,0)$ is not in the function class. If $h_a(x_1)=1$ and $h_a(x_2)=0$, then $x_1<x_2$. So $b_0$ is always smaller than $b_1$.







          share|cite|improve this answer












          share|cite|improve this answer



          share|cite|improve this answer










          answered Jan 15 at 20:06









          Micky MesserMicky Messer

          287




          287












          • $begingroup$
            That answers $1$ and $2$. Do you have any idea about $3$? I can't see why those conditions are sufficient.
            $endgroup$
            – Oliver G
            Jan 16 at 15:34










          • $begingroup$
            Recall that at $a^*$ the loss is zero. If you move the threshold to $a_0$ or $a_1$, the loss will be $epsilon$. Take into account that the loss funtion is monotonous (in this case, not in general) and you see that it is sufficient
            $endgroup$
            – Micky Messer
            Jan 19 at 8:51


















          • $begingroup$
            That answers $1$ and $2$. Do you have any idea about $3$? I can't see why those conditions are sufficient.
            $endgroup$
            – Oliver G
            Jan 16 at 15:34










          • $begingroup$
            Recall that at $a^*$ the loss is zero. If you move the threshold to $a_0$ or $a_1$, the loss will be $epsilon$. Take into account that the loss funtion is monotonous (in this case, not in general) and you see that it is sufficient
            $endgroup$
            – Micky Messer
            Jan 19 at 8:51
















          $begingroup$
          That answers $1$ and $2$. Do you have any idea about $3$? I can't see why those conditions are sufficient.
          $endgroup$
          – Oliver G
          Jan 16 at 15:34




          $begingroup$
          That answers $1$ and $2$. Do you have any idea about $3$? I can't see why those conditions are sufficient.
          $endgroup$
          – Oliver G
          Jan 16 at 15:34












          $begingroup$
          Recall that at $a^*$ the loss is zero. If you move the threshold to $a_0$ or $a_1$, the loss will be $epsilon$. Take into account that the loss funtion is monotonous (in this case, not in general) and you see that it is sufficient
          $endgroup$
          – Micky Messer
          Jan 19 at 8:51




          $begingroup$
          Recall that at $a^*$ the loss is zero. If you move the threshold to $a_0$ or $a_1$, the loss will be $epsilon$. Take into account that the loss funtion is monotonous (in this case, not in general) and you see that it is sufficient
          $endgroup$
          – Micky Messer
          Jan 19 at 8:51


















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