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udf_slope.cc
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udf_slope.cc
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/*
returns the slope of the linear regression function of a data set
input parameters:
dependent data (real)
independent data (real)
number of decimals in result (int, optional)
output:
slope of the linear regression function (real)
registering the function:
CREATE AGGREGATE FUNCTION slope RETURNS REAL SONAME 'udf_slope.so';
getting rid of the function:
DROP FUNCTION slope;
*/
#ifdef STANDARD
#include <stdio.h>
#include <string.h>
#ifdef __WIN__
typedef unsigned __int64 ulonglong;
typedef __int64 longlong;
#else
typedef unsigned long long ulonglong;
typedef long long longlong;
#endif /*__WIN__*/
#else
#include <my_global.h>
#include <my_sys.h>
#endif
#include <mysql.h>
#include <m_ctype.h>
#include <m_string.h>
#define BUFFERSIZE 1024
extern "C" {
my_bool slope_init( UDF_INIT* initid, UDF_ARGS* args, char* message );
void slope_deinit( UDF_INIT* initid );
void slope_clear(UDF_INIT *initid, char *is_null, char *is_error);
void slope_reset( UDF_INIT* initid, UDF_ARGS* args, char* is_null, char *error );
void slope_add( UDF_INIT* initid, UDF_ARGS* args, char* is_null, char *error );
double slope( UDF_INIT* initid, UDF_ARGS* args, char* is_null, char *error );
}
struct regression_data
{
unsigned long count;
unsigned long abscount;
unsigned long pages;
double *valuesx;
double *valuesy;
};
my_bool slope_init( UDF_INIT* initid, UDF_ARGS* args, char* message )
{
if (args->arg_count < 2 || args->arg_count>3)
{
strcpy(message,"wrong number of arguments: slope() requires two or three arguments");
return 1;
}
if (args->arg_type[0]!=REAL_RESULT && args->arg_type[0]!=DECIMAL_RESULT)
{
strcpy(message,"slope() requires a real or decimal as parameter 1");
return 1;
}
if (args->arg_type[1]!=REAL_RESULT && args->arg_type[1]!=DECIMAL_RESULT)
{
strcpy(message,"slope() requires a real or decimal as parameter 2");
return 1;
}
if (args->arg_count>2 && (args->arg_type[2]!=INT_RESULT))
{
strcpy(message,"slope() requires an int as parameter 3");
return 1;
}
initid->decimals=2;
if (args->arg_count==3 && (*((ulong*)args->args[2])<=16))
{
initid->decimals=*((ulong*)args->args[2]);
}
regression_data *buffer = new regression_data;
buffer->count = 0;
buffer->abscount=0;
buffer->pages = 1;
buffer->valuesx = NULL;
buffer->valuesy = NULL;
initid->maybe_null = 1;
initid->max_length = 32;
initid->ptr = (char*)buffer;
return 0;
}
void slope_deinit( UDF_INIT* initid )
{
regression_data *buffer = (regression_data*)initid->ptr;
if (buffer->valuesx != NULL)
{
free(buffer->valuesx);
buffer->valuesx=NULL;
}
if (buffer->valuesy != NULL)
{
free(buffer->valuesy);
buffer->valuesy=NULL;
}
delete initid->ptr;
}
void slope_clear(UDF_INIT *initid, char *is_null, char *is_error)
{
regression_data *buffer = (regression_data*)initid->ptr;
buffer->count = 0;
buffer->abscount=0;
buffer->pages = 1;
*is_null = 0;
*is_error = 0;
if (buffer->valuesx != NULL)
{
free(buffer->valuesx);
buffer->valuesx=NULL;
}
if (buffer->valuesy !=NULL)
{
free(buffer->valuesy);
buffer->valuesy=NULL;
}
buffer->valuesx=(double *) malloc(BUFFERSIZE*sizeof(double));
buffer->valuesy=(double *) malloc(BUFFERSIZE*sizeof(double));
}
void slope_reset( UDF_INIT* initid, UDF_ARGS* args, char* is_null, char* is_error )
{
slope_clear(initid, is_null, is_error);
slope_add( initid, args, is_null, is_error );
}
static double parse_arg(UDF_ARGS *args, int index)
{
if (args->arg_type[index] == REAL_RESULT) {
return *((double*)args->args[index]);
} else {
double ret;
char *str;
str = (char *) malloc(args->lengths[index] + 1);
strncpy(str, args->args[index], args->lengths[index]);
str[args->lengths[index]] = '\0';
sscanf(str, "%lf", &ret);
free(str);
return ret;
}
}
void slope_add( UDF_INIT* initid, UDF_ARGS* args, char* is_null, char* is_error )
{
if (args->args[0]!=NULL && args->args[1]!=NULL)
{
regression_data *buffer = (regression_data*)initid->ptr;
if (buffer->count>=BUFFERSIZE)
{
buffer->pages++;
buffer->count=0;
buffer->valuesx=(double *) realloc(buffer->valuesx,BUFFERSIZE*buffer->pages*sizeof(double));
buffer->valuesy=(double *) realloc(buffer->valuesy,BUFFERSIZE*buffer->pages*sizeof(double));
}
buffer->valuesx[buffer->abscount] = parse_arg(args, 0);
buffer->valuesy[buffer->abscount] = parse_arg(args, 1);
buffer->abscount++;
buffer->count++;
}
}
double slope( UDF_INIT* initid, UDF_ARGS* args, char* is_null, char* is_error )
{
regression_data* buffer = (regression_data*)initid->ptr;
if (buffer->abscount==0 || *is_error!=0)
{
*is_null = 1;
return 0.0;
}
ulong i;
double xmean=0.0; double ymean=0.0; double xxsum=0.0; double xysum=0.0; double xvalue; double yvalue;
for (i=0;i<buffer->abscount;++i)
{
xmean+=buffer->valuesx[i];
ymean+=buffer->valuesy[i];
}
xmean/=buffer->abscount;
ymean/=buffer->abscount;
for (i=0;i<buffer->abscount;++i)
{
xvalue=buffer->valuesx[i]-xmean;
yvalue=buffer->valuesy[i]-ymean;
xxsum+=xvalue*xvalue;
xysum+=xvalue*yvalue;
}
if (xxsum!=0.0)
{
*is_null=0;
return xysum/xxsum;
} else
{
*is_null=1;
return 0.0;
}
}