journey of Froakie (ケロマツの旅路)

Introduction 日本語 ver Today, I will explain MAP estimation(maximum a posteriori estimation). MAP estimation is used Bayes' thorem. If sample data is few, we can not belive value by Maximum likelihood estimation. Then, MAP estimation is enable to include our sense.  Overveiw Bayes' theorem MAP estimation Conjugate distribution Bayes' theorem  Bayes' theorem is $$P(A|B) = \frac{P(B|A)P(A)}{P(B)}$$ $P(A|B)$ is Probability when B occur. Please go on  http://takutori.blogspot.com/2018/04/bayes-theorem.html to know detail of Bayes' theorem. Map estimation Map estimation is used Bayes' theorem. Map estimation estimate parameter of population by maximuzing posterior probability. Now, suppoce we get data $x_1,x_2,...,x_n$ from population which have parameter $\theta$. Then, we want to $P(\theta|x_1,x_2,...,x_n)$. Here, we use Bayes' theorem. $$P(\theta|x_1,x_2,...,x_n) = \frac{P(x_1,x_2,...,x_n | \theta ) P(\theta)}{P(x_1,x_2,...,x_n)}

問題 English ver 次のようなクエ リーをプロシージャーの中で使いたかった。 SET @user_variable = FLOOR(RAND()*10); INSERT INTO  Table_name (columns_name) VALUES (1) FROM Table_name ORDER BY RAND() LIMIT 1 OFFSET @user_variable; これはランダムに行を入れ替えたテーブルの上から@user_variable番目の行のcolumns_nameに1を入れることをしたかった。しかし、うまくいかなかった。その原因はLIMITやOFFSETは後ろにユーザー変数を持ってこれないことにあった。 解決法 次のようにするとうまくいく。 SET @user_variable = FLOOR(RAND()*10); PREPARE SET_STMT FROM 'INSERT INTO  Table_name (columns_name) VALUES (1) FROM Table_name ORDER BY RAND() LIMIT 1 OFFSET ?;';  EXECUTE SET_STMT USING @user_variable; 結論、やりたい操作を''で囲って上のようなことを書けばLIMITでもOFFSETでもうまくいく。 Reference http://techtipshoge.blogspot.com/2011/10/limit.html

Problem 日本語 ver I want to use this query in PROCEDURE. SET @user_variable = FLOOR(RAND()*10); INSERT INTO  Table_name (columns_name) VALUES (1) FROM Table_name ORDER BY RAND() LIMIT 1 OFFSET @user_variable; This query want to substitute 1 for the @user_variable 'th line of columns_name, but this query does not work. A cause is that LIMIT and OFFSET does not user variable. Solution SET @user_variable = FLOOR(RAND()*10); PREPARE SET_STMT FROM 'INSERT INTO  Table_name (columns_name) VALUES (1) FROM Table_name ORDER BY RAND() LIMIT 1 OFFSET ?;';  EXECUTE SET_STMT USING @user_variable; Conclusion, if you want to use user variable with LIMIT or OFFSET, use PREPARE STATMENT. Reference http://techtipshoge.blogspot.com/2011/10/limit.html