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pearson.c
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pearson.c
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#include <stddef.h>
#include <stdio.h>
#include <assert.h>
#include <math.h>
#include <sqlite3.h>
#include "pearson.h"
void validateTypes(sqlite3_context *context, int a, int b) {
if (a == SQLITE_NULL || b == SQLITE_NULL) {
sqlite3_result_error(context, "Null types.", -1);
}
if ((a != SQLITE_INTEGER && a != SQLITE_FLOAT) || a != b) {
sqlite3_result_error(context, "Incompatible types.", -1);
}
}
void pearsonStep(sqlite3_context *context, int argc, sqlite3_value **argv){
PrsCtx *p;
int xType, yType;
p = sqlite3_aggregate_context(context, sizeof(*p));
xType = sqlite3_value_numeric_type(argv[0]);
yType = sqlite3_value_numeric_type(argv[1]);
validateTypes(context, xType, yType);
if(p){
p->count++;
double x, y;
if(xType == SQLITE_INTEGER ){
x = (double) sqlite3_value_int64(argv[0]);
y = (double) sqlite3_value_int64(argv[1]);
} else {
x = sqlite3_value_double(argv[0]);
y = sqlite3_value_double(argv[1]);
}
p->x_sum += x;
p->y_sum += y;
p->prod += x * y;
p->x_sqr += x * x;
p->y_sqr += y * y;
}
}
double pearson(PrsCtx *p) {
int n = p->count;
double top = p->prod - (p->x_sum*p->y_sum / n),
x_b = p->x_sqr - (p->x_sum*p->x_sum / n),
y_b = p->y_sqr - (p->y_sum*p->y_sum / n);
return top/sqrt(x_b * y_b);
}
void pearsonFinalize(sqlite3_context *context){
PrsCtx *p;
p = sqlite3_aggregate_context(context, 0);
if(!p || p->count <= 0) {
sqlite3_result_error(context, "Error calculating value.", -1);
}
sqlite3_result_double(context, pearson(p));
}