Question

How do you pass the correct value to udf_slope's second parameter type?

Attempts

• CAST(Y.YEAR AS FLOAT), but that failed (SQL error).
• Y.YEAR + 0.0, but that failed, too (see error message).
• slope(D.AMOUNT, 1.0), failed as well

Error Message

Using udf_slope fails due to:

Can't initialize function 'slope'; slope() requires a real as parameter 2

Code

SELECT
  D.AMOUNT,
  Y.YEAR,
  slope(D.AMOUNT, Y.YEAR + 0.0) as SLOPE,
  intercept(D.AMOUNT, Y.YEAR + 0.0) as INTERCEPT
FROM
  YEAR_REF Y,
  DAILY D

Here, D.AMOUNT is a FLOAT and Y.YEAR is an INTEGER.

Create Function

The slope function was created as follows:

CREATE AGGREGATE FUNCTION slope RETURNS REAL SONAME 'udf_slope.so';

Function Signature

From udf_slope.cc:

double slope( UDF_INIT* initid, UDF_ARGS* args, char* is_null, char* is_error )

Example Usages

Reading the fine manual reveals:

UDF intercept() Calculates the intercept of the linear regression of two sets of variables.

Function name   intercept
Input parameter(s)  2 (dependent variable: REAL, independent variable: REAL)
Examples        SELECT intercept(income,age) FROM customers

UDF slope() Calculates the slope of the linear regression of two sets of variables.

Function name   slope
Input parameter(s)  2 (dependent variable: REAL, independent variable: REAL)
Examples        SELECT slope(income,age) FROM customers

Thoughts?

Thank you!