Bayes Thereom – broken down


To arrive at an understanding of Bayes Theorem, we begin with the

Definition of a conditional probability

P(A|B) = translates to “The probability of A happening, given that event B has occurred”.

P(A|B) can be rewritten like

P(A | B) = P(A ∩ B)

                ————

                   P(B)

 

Also, P(A ∩ B) = P(A | B) × P(B) (i.e. the probability of A and B).

And because P(A ∩ B) = can also be expressed as P(B ∩ A)

We can say  P(B ∩ A) = P(B | A) × P(A)

Therefore, we can also express “the probability of A happening given event B” as

P(A | B) = P(B | A) × P(A)

                ——————–

                       P(B)

 

We can further expand the probability of B by writing it as

P(B) = P(A) × P(B | A) + P(Al) × P(B | Al )

(in normal language, the probability of B is equal to the probability of A multiplied by the probability of A given B, plus the probability of the complement of A multiplied by the probability of the complement of A given B)

 

Thus resulting in the Law of Total Probability.  

This law enables us to find the total probability of a particular event based on conditional probabilities.  Also, our new expression can be substituted into our formula for “the probability of A happening given event B” as the denominator to give us Bayes Theorem.

Bayes Theorem provides a means of finding reverse conditional probabilities when you don’t know every probability up front.

 

Bayes Theorem

P(A | B) =                     P(A) × P(B | A)

                     ——————————-

                      P(A) × P(B | A) + P(Al) × P(B | Al)

Leave a comment

Filed under Math, Sharing Stuff

tPostgresqlOutput_3 org.postgresql.util.PSQLException: ERROR: length for type varchar must be at least 1


There are several reasons why you may receive this error when using Talend Open Studio, but the one I recently encountered was user error.  When I created my schema, I had placed my varchar length values under the “Precision” column instead of “Length” column.  This was the cause of my error.

Misplaced varchar lengths in Talend Open Studio schema

I prefer these errors over product bugs!

 

 

Leave a comment

Filed under SQL

Listing out Built in Functions in Python


To retrieve a list of Built in Functions in Python, type:  dir(__builtins__)

You will get the following list

Firefox_Screenshot_2016-01-31T04-16-41.818Z

To understand what each function does, you can type help(fuction_name) to get more details on that function.  Example: help(NameError)

Firefox_Screenshot_2016-01-31T04-20-36.900Z

 

Leave a comment

Filed under Computer - Technical, Python

List of Built in Functions in Python


To get a list of built in functions in Python, type the following:

It will result in a list like the one below

 

 

Leave a comment

Filed under Sharing Stuff

Talend Data Integration – Exception in component tOracleOutput_1java.lang.ArrayIndexOutOfBoundsException: -32703


You are probably seeing this error as you attempt to transfer data with many date values from one Oracle database to another Oracle database using Talend Studio.

Well quick fix (not sure why it works) is to decrease the commit size in your OracleOutput node. The default is 10,000.  I reduced mine to 500.  See illustration below.

Changing Commit In Talend Data Integration

Comments are always welcome.

Leave a comment

Filed under SQL

Talend Data Integration – Exception in component tOracleOutput_1java.sql.SQLException: ORA-01727: numeric precision specifier is out of range (1 to 38)


When you receive an out of range (1 to 38) error while importing from one Oracle DB to another Oracle DB

  1. Go to your tMap
    tMap
  2. Locate Big Decimals and any other precision numeric values.
  3. Be sure to fill in blanks.
  4. Save your job and re-run

Fin (I hope)

Leave a comment

Filed under Sharing Stuff

update DB2 table with values from another table


Situation Text to be written later.

UPDATE TABLE01 T1
SET (T1.FIELD01, T1.FIELD02)
=
(SELECT CROSS_FIELD_01, CROSS_FIELD02
FROM TABLE02 T2
WHERE T2.MATCHING_FIELD = T1.MATCHING_FIELD
)

End of code text

Leave a comment

Filed under Sharing Stuff