#include "pool.h"
#include "hash.h"
#include "stats.h"
+#include "t-test.h"
+#include "levene.h"
/* (specification)
"T-TEST" (tts_):
static struct cmd_t_test cmd;
-
static struct pool *t_test_pool ;
/* Variable for the GROUPS subcommand, if given. */
/* GROUPS: Number of values specified by the user; the values
specified if any. */
+
static int n_groups_values;
static union value groups_values[2];
+
/* PAIRS: Number of pairs to be compared ; each pair. */
static int n_pairs = 0 ;
struct pair
/* A function to create, populate and submit the Paired Samples Correlation
box */
-void pscbox(struct cmd_t_test *cmd);
+void pscbox(void);
/* Structures and Functions for the Test Results Box */
};
-static int common_calc (struct ccase *);
-static void common_precalc (void);
-static void common_postcalc (void);
+static int common_calc (struct ccase *, void *);
+static void common_precalc (void *);
+static void common_postcalc (void *);
-static int one_sample_calc (struct ccase *);
-static void one_sample_precalc (void);
-static void one_sample_postcalc (void);
+static int one_sample_calc (struct ccase *, void *);
+static void one_sample_precalc (void *);
+static void one_sample_postcalc (void *);
+
+static int paired_calc (struct ccase *, void *);
+static void paired_precalc (void *);
+static void paired_postcalc (void *);
+
+static void group_precalc (void *);
+static int group_calc (struct ccase *, void *);
+static void group_postcalc (void *);
-static int paired_calc (struct ccase *);
-static void paired_precalc (void);
-static void paired_postcalc (void);
static int compare_var_name (const void *a_, const void *b_, void *v_ UNUSED);
static unsigned hash_var_name (const void *a_, void *v_ UNUSED);
+
int
cmd_t_test(void)
{
}
- procedure(common_precalc,common_calc,common_postcalc);
+ procedure(common_precalc,common_calc,common_postcalc, NULL);
switch(mode)
{
case T_1_SAMPLE:
- procedure(one_sample_precalc,one_sample_calc,one_sample_postcalc);
+ procedure(one_sample_precalc,one_sample_calc,one_sample_postcalc, NULL);
break;
case T_PAIRED:
- procedure(paired_precalc,paired_calc,paired_postcalc);
+ procedure(paired_precalc,paired_calc,paired_postcalc, NULL);
+ break;
+ case T_IND_SAMPLES:
+ procedure(group_precalc,group_calc,group_postcalc, NULL);
+ levene(groups, cmd.n_variables, cmd.v_variables);
break;
}
-
t_test_pool = pool_create ();
ssbox_finalize(&stat_summary_box);
if ( mode == T_PAIRED)
- {
- pscbox(&cmd);
- }
+ pscbox();
trbox_create(&test_results_box,&cmd,mode);
trbox_populate(&test_results_box,&cmd);
n_pairs=0;
free(pairs);
pairs=0;
+
+
+ if ( mode == T_IND_SAMPLES)
+ {
+ int i;
+ /* Destroy any group statistics we created */
+ for (i= 0 ; i < cmd.n_variables ; ++i )
+ {
+ free(cmd.v_variables[i]->p.t_t.gs);
+ }
+ }
return CMD_SUCCESS;
}
for (i=0; i < cmd->n_variables; ++i)
{
+ int g;
+
tab_text (ssb->t, 0, i*2+1, TAB_LEFT, cmd->v_variables[i]->name);
if (val_lab1)
else
tab_float(ssb->t, 1 ,i*2+1, TAB_LEFT, groups_values[0].f, 2,0);
+
if (val_lab2)
tab_text (ssb->t, 1, i*2+1+1, TAB_LEFT, val_lab2);
else
tab_float(ssb->t, 1 ,i*2+1+1, TAB_LEFT, groups_values[1].f,2,0);
+
+ /* Fill in the group statistics */
+ for ( g=0; g < 2 ; ++g )
+ {
+ struct group_statistics *gs = &cmd->v_variables[i]->p.t_t.gs[g];
+
+ tab_float(ssb->t, 2 ,i*2+g+1, TAB_RIGHT, gs->n, 2, 0);
+ tab_float(ssb->t, 3 ,i*2+g+1, TAB_RIGHT, gs->mean, 8, 2);
+ tab_float(ssb->t, 4 ,i*2+g+1, TAB_RIGHT, gs->std_dev, 8, 3);
+ tab_float(ssb->t, 5 ,i*2+g+1, TAB_RIGHT, gs->se_mean, 8, 3);
+ }
}
}
for (j=0 ; j < 2 ; ++j)
{
- struct t_test_proc *ttp;
+ struct group_statistics *gs;
- ttp=&pairs[i].v[j]->p.t_t;
+ gs=&pairs[i].v[j]->p.t_t.ugs;
/* Titles */
tab_text (ssb->t, 1, i*2+j+1, TAB_LEFT, pairs[i].v[j]->name);
/* Values */
- tab_float (ssb->t,2, i*2+j+1, TAB_RIGHT, ttp->mean, 8, 2);
- tab_float (ssb->t,3, i*2+j+1, TAB_RIGHT, ttp->n, 2, 0);
- tab_float (ssb->t,4, i*2+j+1, TAB_RIGHT, ttp->std_dev, 8, 3);
- tab_float (ssb->t,5, i*2+j+1, TAB_RIGHT, ttp->se_mean, 8, 3);
+ tab_float (ssb->t,2, i*2+j+1, TAB_RIGHT, gs->mean, 8, 2);
+ tab_float (ssb->t,3, i*2+j+1, TAB_RIGHT, gs->n, 2, 0);
+ tab_float (ssb->t,4, i*2+j+1, TAB_RIGHT, gs->std_dev, 8, 3);
+ tab_float (ssb->t,5, i*2+j+1, TAB_RIGHT, gs->se_mean, 8, 3);
}
for (i=0; i < cmd->n_variables; ++i)
{
- struct t_test_proc *ttp;
- ttp= &cmd->v_variables[i]->p.t_t;
+ struct group_statistics *gs;
+ gs= &cmd->v_variables[i]->p.t_t.ugs;
tab_text (ssb->t, 0, i+1, TAB_LEFT, cmd->v_variables[i]->name);
- tab_float (ssb->t,1, i+1, TAB_RIGHT, ttp->n, 2, 0);
- tab_float (ssb->t,2, i+1, TAB_RIGHT, ttp->mean, 8, 2);
- tab_float (ssb->t,3, i+1, TAB_RIGHT, ttp->std_dev, 8, 2);
- tab_float (ssb->t,4, i+1, TAB_RIGHT, ttp->se_mean, 8, 3);
+ tab_float (ssb->t,1, i+1, TAB_RIGHT, gs->n, 2, 0);
+ tab_float (ssb->t,2, i+1, TAB_RIGHT, gs->mean, 8, 2);
+ tab_float (ssb->t,3, i+1, TAB_RIGHT, gs->std_dev, 8, 2);
+ tab_float (ssb->t,4, i+1, TAB_RIGHT, gs->se_mean, 8, 3);
}
}
tab_hline(self->t,TAL_1, hsize-2,hsize-1,2);
tab_box(self->t,-1,-1,-1,TAL_1, hsize-2,2,hsize-1,vsize-1);
tab_joint_text(self->t, 2, 0, 3, 0,
- TAB_CENTER,_("Levine's Test for Equality of Variances"));
+ TAB_CENTER,_("Levene's Test for Equality of Variances"));
tab_joint_text(self->t, 4,0,hsize-1,0,
TAB_CENTER,_("t-test for Equality of Means"));
assert(self);
for (i=0; i < cmd->n_variables; ++i)
{
+ int which =1;
+ double p,q;
+ int status;
+ double bound;
+
+ double t;
+ double df;
+
+ double df1, df2;
+
+ double pooled_variance;
+ double std_err_diff;
+ double mean_diff;
+
+ struct group_statistics *gs0 = &cmd->v_variables[i]->p.t_t.gs[0];
+ struct group_statistics *gs1 = &cmd->v_variables[i]->p.t_t.gs[1];
+
tab_text (self->t, 0, i*2+3, TAB_LEFT, cmd->v_variables[i]->name);
tab_text (self->t, 1, i*2+3, TAB_LEFT, _("Equal variances assumed"));
+
+ tab_float(self->t, 2, i*2+3, TAB_CENTER,
+ cmd->v_variables[i]->p.t_t.levene, 8,3);
+
+
+ /* Now work out the significance of the Levene test */
+
+ which=1; df1 = 1; df2 = cmd->v_variables[i]->p.t_t.ugs.n - 2;
+ cdff(&which,&p,&q,&cmd->v_variables[i]->p.t_t.levene,
+ &df1,&df2,&status,&bound);
+
+ if ( 0 != status )
+ {
+ msg( SE, _("Error calculating F statistic (cdff returned %d)."),status);
+ }
+
+ tab_float(self->t, 3, i*2+3, TAB_CENTER, q, 8,3 );
+
+ df = gs0->n + gs1->n - 2.0 ;
+ tab_float (self->t, 5, i*2+3, TAB_RIGHT, df, 2, 0);
+
+ pooled_variance = ( (gs0->n )*sqr(gs0->s_std_dev)
+ +
+ (gs1->n )*sqr(gs1->s_std_dev)
+ ) / df ;
+
+ t = (gs0->mean - gs1->mean) / sqrt(pooled_variance) ;
+ t /= sqrt((gs0->n + gs1->n)/(gs0->n*gs1->n));
+
+ tab_float (self->t, 4, i*2+3, TAB_RIGHT, t, 8, 3);
+
+
+ which=1; /* get p & q from t & df */
+ cdft(&which, &p, &q, &t, &df, &status, &bound);
+ if ( 0 != status )
+ {
+ msg( SE, _("Error calculating T statistic (cdft returned %d)."),status);
+ }
+
+ tab_float(self->t, 6, i*2+3, TAB_RIGHT, 2.0*(t>0?q:p) , 8, 3);
+
+ mean_diff = gs0->mean - gs1->mean;
+ tab_float(self->t, 7, i*2+3, TAB_RIGHT, mean_diff, 8, 3);
+
+
+ std_err_diff = sqrt( sqr(gs0->se_mean) + sqr(gs1->se_mean));
+ tab_float(self->t, 8, i*2+3, TAB_RIGHT, std_err_diff, 8, 3);
+
+
+ /* Now work out the confidence interval */
+ q = (1 - cmd->criteria)/2.0; /* 2-tailed test */
+ p = 1 - q ;
+ which=2; /* Calc T from p,q and df */
+ cdft(&which, &p, &q, &t, &df, &status, &bound);
+ if ( 0 != status )
+ {
+ msg( SE, _("Error calculating T statistic (cdft returned %d)."),status);
+ }
+
+ tab_float(self->t, 9, i*2+3, TAB_RIGHT,
+ mean_diff - t * std_err_diff, 8, 3);
+
+ tab_float(self->t, 10, i*2+3, TAB_RIGHT,
+ mean_diff + t * std_err_diff, 8, 3);
+
+
+ {
+ double se2;
+ /* Now for the \sigma_1 != \sigma_2 case */
tab_text (self->t, 1, i*2+3+1,
TAB_LEFT, _("Equal variances not assumed"));
+
+
+ se2 = (sqr(gs0->s_std_dev)/(gs0->n -1) ) +
+ (sqr(gs1->s_std_dev)/(gs1->n -1) );
+
+ t = mean_diff / sqrt(se2) ;
+ tab_float (self->t, 4, i*2+3+1, TAB_RIGHT, t, 8, 3);
+
+ df = sqr(se2) / (
+ (sqr(sqr(gs0->s_std_dev)/(gs0->n - 1 ))
+ /(gs0->n -1 )
+ )
+ +
+ (sqr(sqr(gs1->s_std_dev)/(gs1->n - 1 ))
+ /(gs1->n -1 )
+ )
+ ) ;
+ tab_float (self->t, 5, i*2+3+1, TAB_RIGHT, df, 8, 3);
+
+ which=1; /* get p & q from t & df */
+ cdft(&which, &p, &q, &t, &df, &status, &bound);
+ if ( 0 != status )
+ {
+ msg( SE, _("Error calculating T statistic (cdft returned %d)."),status);
+ }
+
+ tab_float(self->t, 6, i*2+3+1, TAB_RIGHT, 2.0*(t>0?q:p) , 8, 3);
+
+ /* Now work out the confidence interval */
+ q = (1 - cmd->criteria)/2.0; /* 2-tailed test */
+ p = 1 - q ;
+ which=2; /* Calc T from p,q and df */
+ cdft(&which, &p, &q, &t, &df, &status, &bound);
+ if ( 0 != status )
+ {
+ msg( SE, _("Error calculating T statistic (cdft returned %d)."),status);
+ }
+
+
+ tab_float(self->t, 7, i*2+3+1, TAB_RIGHT, mean_diff, 8, 3);
+
+
+ tab_float(self->t, 8, i*2+3+1, TAB_RIGHT, std_err_diff, 8, 3);
+
+
+ tab_float(self->t, 9, i*2+3+1, TAB_RIGHT,
+ mean_diff - t * std_err_diff, 8, 3);
+
+ tab_float(self->t, 10, i*2+3+1, TAB_RIGHT,
+ mean_diff + t * std_err_diff, 8, 3);
+
+ }
}
}
struct variable *v0 = pairs[i].v[0];
struct variable *v1 = pairs[i].v[1];
- struct t_test_proc *ttp0 = &v0->p.t_t;
- struct t_test_proc *ttp1 = &v1->p.t_t;
+ struct group_statistics *gs0 = &v0->p.t_t.ugs;
+ struct group_statistics *gs1 = &v1->p.t_t.ugs;
- double n = ttp0->n;
+ double n = gs0->n;
double t;
double df = n - 1;
tab_float(trb->t, 6, i+3, TAB_RIGHT,
pairs[i].mean_diff + t * se_mean , 8, 4);
- t = ( ttp0->mean - ttp1->mean)
+ t = ( gs0->mean - gs1->mean)
/ sqrt (
- ( sqr(ttp0->s_std_dev) + sqr(ttp1->s_std_dev) -
- 2 * pairs[i].correlation * ttp0->s_std_dev * ttp1->s_std_dev )
+ ( sqr(gs0->s_std_dev) + sqr(gs1->s_std_dev) -
+ 2 * pairs[i].correlation * gs0->s_std_dev * gs1->s_std_dev )
/ (n-1) )
;
}
- tab_float(trb->t, 9, i+3, TAB_RIGHT, p*2.0 , 8, 3);
-
+ tab_float(trb->t, 9, i+3, TAB_RIGHT, 2.0*(t>0?q:p) , 8, 3);
}
-
}
/* Initialize the one sample trbox */
double df;
int status;
double bound;
- struct t_test_proc *ttp;
- ttp= &cmd->v_variables[i]->p.t_t;
+ struct group_statistics *gs;
+ gs= &cmd->v_variables[i]->p.t_t.ugs;
tab_text (trb->t, 0, i+3, TAB_LEFT, cmd->v_variables[i]->name);
- t = (ttp->mean - cmd->n_testval ) * sqrt(ttp->n) / ttp->std_dev ;
+ t = (gs->mean - cmd->n_testval ) * sqrt(gs->n) / gs->std_dev ;
tab_float (trb->t, 1, i+3, TAB_RIGHT, t, 8,3);
/* degrees of freedom */
- df = ttp->n - 1;
+ df = gs->n - 1;
tab_float (trb->t, 2, i+3, TAB_RIGHT, df, 8,0);
}
- /* Multiply by 2 to get 2-tailed significance */
- tab_float (trb->t, 3, i+3, TAB_RIGHT, q*2.0, 8,3);
+ /* Multiply by 2 to get 2-tailed significance, makeing sure we've got
+ the correct tail*/
+ tab_float (trb->t, 3, i+3, TAB_RIGHT, 2.0*(t>0?q:p), 8,3);
- tab_float (trb->t, 4, i+3, TAB_RIGHT, ttp->mean_diff, 8,3);
+ tab_float (trb->t, 4, i+3, TAB_RIGHT, gs->mean_diff, 8,3);
q = (1 - cmd->criteria)/2.0; /* 2-tailed test */
}
tab_float (trb->t, 5, i+3, TAB_RIGHT,
- ttp->mean_diff - t * ttp->se_mean, 8,4);
+ gs->mean_diff - t * gs->se_mean, 8,4);
tab_float (trb->t, 6, i+3, TAB_RIGHT,
- ttp->mean_diff + t * ttp->se_mean, 8,4);
+ gs->mean_diff + t * gs->se_mean, 8,4);
}
}
/* Create , populate and submit the Paired Samples Correlation box */
void
-pscbox(struct cmd_t_test *cmd)
+pscbox(void)
{
const int rows=1+n_pairs;
const int cols=5;
tab_text(table, 3,0, TAB_CENTER | TAT_TITLE, _("Correlation"));
tab_text(table, 4,0, TAB_CENTER | TAT_TITLE, _("Sig."));
-
for (i=0; i < n_pairs; ++i)
{
int which =1;
int status;
double bound;
- double df = pairs[i].v[0]->p.t_t.n -2;
+ double df = pairs[i].v[0]->p.t_t.ugs.n -2;
double correlation_t =
pairs[i].correlation * sqrt(df) /
/* row data */
tab_float(table, 3, i+1, TAB_RIGHT, pairs[i].correlation, 8, 3);
- tab_float(table, 2, i+1, TAB_RIGHT, pairs[i].v[0]->p.t_t.n , 4, 0);
+ tab_float(table, 2, i+1, TAB_RIGHT, pairs[i].v[0]->p.t_t.ugs.n , 4, 0);
cdft(&which, &p, &q, &correlation_t, &df, &status, &bound);
}
- tab_float(table, 4, i+1, TAB_RIGHT, q*2.0, 8, 3);
-
-
-
+ tab_float(table, 4, i+1, TAB_RIGHT, 2.0*(correlation_t>0?q:p), 8, 3);
}
/* Per case calculations common to all variants of the T test */
static int
-common_calc (struct ccase *c)
+common_calc (struct ccase *c, void *aux UNUSED)
{
int i;
for(i=0; i< cmd.n_variables ; ++i)
{
- struct t_test_proc *ttp;
+ struct group_statistics *gs;
struct variable *v = cmd.v_variables[i];
union value *val = &c->data[v->fv];
- ttp= &cmd.v_variables[i]->p.t_t;
+ gs= &cmd.v_variables[i]->p.t_t.ugs;
if (val->f != SYSMIS)
{
- ttp->n+=weight;
- ttp->sum+=weight * val->f;
- ttp->ssq+=weight * val->f * val->f;
+ gs->n+=weight;
+ gs->sum+=weight * val->f;
+ gs->ssq+=weight * val->f * val->f;
}
}
return 0;
/* Pre calculations common to all variants of the T test */
static void
-common_precalc (void)
+common_precalc (void *aux UNUSED)
{
int i=0;
for(i=0; i< cmd.n_variables ; ++i)
{
- struct t_test_proc *ttp;
- ttp= &cmd.v_variables[i]->p.t_t;
+ struct group_statistics *gs;
+ gs= &cmd.v_variables[i]->p.t_t.ugs;
- ttp->sum=0;
- ttp->n=0;
- ttp->ssq=0;
- ttp->sum_diff=0;
+ gs->sum=0;
+ gs->n=0;
+ gs->ssq=0;
+ gs->sum_diff=0;
}
}
/* Post calculations common to all variants of the T test */
void
-common_postcalc (void)
+common_postcalc (void *aux UNUSED)
{
int i=0;
for(i=0; i< cmd.n_variables ; ++i)
{
- struct t_test_proc *ttp;
- ttp= &cmd.v_variables[i]->p.t_t;
+ struct group_statistics *gs;
+ gs= &cmd.v_variables[i]->p.t_t.ugs;
- ttp->mean=ttp->sum / ttp->n;
- ttp->s_std_dev= sqrt(
- ( (ttp->ssq / ttp->n ) - ttp->mean * ttp->mean )
+ gs->mean=gs->sum / gs->n;
+ gs->s_std_dev= sqrt(
+ ( (gs->ssq / gs->n ) - gs->mean * gs->mean )
) ;
- ttp->std_dev= sqrt(
- ttp->n/(ttp->n-1) *
- ( (ttp->ssq / ttp->n ) - ttp->mean * ttp->mean )
+ gs->std_dev= sqrt(
+ gs->n/(gs->n-1) *
+ ( (gs->ssq / gs->n ) - gs->mean * gs->mean )
) ;
- ttp->se_mean = ttp->std_dev / sqrt(ttp->n);
- ttp->mean_diff= ttp->sum_diff / ttp->n;
+ gs->se_mean = gs->std_dev / sqrt(gs->n);
+ gs->mean_diff= gs->sum_diff / gs->n;
}
}
/* Per case calculations for one sample t test */
static int
-one_sample_calc (struct ccase *c)
+one_sample_calc (struct ccase *c, void *aux UNUSED)
{
int i;
for(i=0; i< cmd.n_variables ; ++i)
{
- struct t_test_proc *ttp;
+ struct group_statistics *gs;
struct variable *v = cmd.v_variables[i];
union value *val = &c->data[v->fv];
- ttp= &cmd.v_variables[i]->p.t_t;
+ gs= &cmd.v_variables[i]->p.t_t.ugs;
if (val->f != SYSMIS)
- ttp->sum_diff += weight * (val->f - cmd.n_testval);
+ gs->sum_diff += weight * (val->f - cmd.n_testval);
}
return 0;
/* Pre calculations for one sample t test */
static void
-one_sample_precalc (void)
+one_sample_precalc (void *aux UNUSED)
{
int i=0;
for(i=0; i< cmd.n_variables ; ++i)
{
- struct t_test_proc *ttp;
- ttp= &cmd.v_variables[i]->p.t_t;
+ struct group_statistics *gs;
+ gs= &cmd.v_variables[i]->p.t_t.ugs;
- ttp->sum_diff=0;
+ gs->sum_diff=0;
}
}
/* Post calculations for one sample t test */
static void
-one_sample_postcalc (void)
+one_sample_postcalc (void *aux UNUSED)
{
int i=0;
for(i=0; i< cmd.n_variables ; ++i)
{
- struct t_test_proc *ttp;
- ttp= &cmd.v_variables[i]->p.t_t;
+ struct group_statistics *gs;
+ gs= &cmd.v_variables[i]->p.t_t.ugs;
- ttp->mean_diff = ttp->sum_diff / ttp->n ;
+ gs->mean_diff = gs->sum_diff / gs->n ;
}
}
}
+
static void
-paired_precalc (void)
+paired_precalc (void *aux UNUSED)
{
int i;
}
+
static int
-paired_calc (struct ccase *c)
+paired_calc (struct ccase *c, void *aux UNUSED)
{
int i;
union value *val0 = &c->data[v0->fv];
union value *val1 = &c->data[v1->fv];
- pairs[i].correlation += ( val0->f - pairs[i].v[0]->p.t_t.mean )
+ pairs[i].correlation += ( val0->f - pairs[i].v[0]->p.t_t.ugs.mean )
*
- ( val1->f - pairs[i].v[1]->p.t_t.mean );
+ ( val1->f - pairs[i].v[1]->p.t_t.ugs.mean );
pairs[i].sum_of_diffs += val0->f - val1->f ;
pairs[i].ssq_diffs += sqr(val0->f - val1->f);
}
-
return 0;
}
static void
-paired_postcalc (void)
+paired_postcalc (void *aux UNUSED)
{
int i;
for(i=0; i < n_pairs ; ++i )
{
- const double n = pairs[i].v[0]->p.t_t.n ;
+ const double n = pairs[i].v[0]->p.t_t.ugs.n ;
- pairs[i].correlation /= pairs[i].v[0]->p.t_t.std_dev *
- pairs[i].v[1]->p.t_t.std_dev ;
- pairs[i].correlation /= pairs[i].v[0]->p.t_t.n -1;
+ pairs[i].correlation /= pairs[i].v[0]->p.t_t.ugs.std_dev *
+ pairs[i].v[1]->p.t_t.ugs.std_dev ;
+ pairs[i].correlation /= pairs[i].v[0]->p.t_t.ugs.n -1;
pairs[i].mean_diff = pairs[i].sum_of_diffs / n ;
-
sqr(pairs[i].mean_diff )
) );
+ }
+}
+
+static int
+get_group(const union value *val, struct variable *var)
+{
+ if ( 0 == compare_values(val,&groups_values[0],var->width) )
+ return 0;
+ else if (0 == compare_values(val,&groups_values[1],var->width) )
+ return 1;
+
+ /* Never reached */
+ assert(0);
+ return -1;
+}
+
+
+static void
+group_precalc (void *aux UNUSED)
+{
+ int i;
+ int j;
+ for(i=0; i< cmd.n_variables ; ++i)
+ {
+ struct t_test_proc *ttpr = &cmd.v_variables[i]->p.t_t;
+
+ /* There's always 2 groups for a T - TEST */
+ ttpr->n_groups = 2;
+ ttpr->gs = xmalloc(sizeof(struct group_statistics) * 2) ;
+
+ for (j=0 ; j < 2 ; ++j)
+ {
+ ttpr->gs[j].sum=0;
+ ttpr->gs[j].n=0;
+ ttpr->gs[j].ssq=0;
+ ttpr->gs[j].id = groups_values[j];
+ }
}
+
}
+
+static int
+group_calc (struct ccase *c, void *aux UNUSED)
+{
+ int i;
+ union value *gv = &c->data[groups->fv];
+
+ double weight = dict_get_case_weight(default_dict,c);
+
+ gv = &c->data[groups->fv];
+
+ for(i=0; i< cmd.n_variables ; ++i)
+ {
+ int g = get_group(gv,groups);
+
+ struct group_statistics *gs = &cmd.v_variables[i]->p.t_t.gs[g];
+
+ union value *val=&c->data[cmd.v_variables[i]->fv];
+
+ gs->n+=weight;
+ gs->sum+=weight * val->f;
+ gs->ssq+=weight * sqr(val->f);
+ }
+
+ return 0;
+}
+
+
+static void
+group_postcalc (void *aux UNUSED)
+{
+ int i;
+ int j;
+
+ for(i=0; i< cmd.n_variables ; ++i)
+ {
+ for (j=0 ; j < 2 ; ++j)
+ {
+ struct group_statistics *gs;
+ gs=&cmd.v_variables[i]->p.t_t.gs[j];
+
+ gs->mean = gs->sum / gs->n;
+
+ gs->s_std_dev= sqrt(
+ ( (gs->ssq / gs->n ) - gs->mean * gs->mean )
+ ) ;
+
+ gs->std_dev= sqrt(
+ gs->n/(gs->n-1) *
+ ( (gs->ssq / gs->n ) - gs->mean * gs->mean )
+ ) ;
+
+ gs->se_mean = gs->std_dev / sqrt(gs->n);
+ }
+ }
+}
+