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include <mach.h>
include <ctype.h>
include <error.h>
include "pdm.h"
# PDM_STATISTICS -- Calculate the sum of squares and the variance of the data.
procedure pdm_statistics (pdmp)
pointer pdmp # pointer to PDM data structure
int npt, i, j
double var, sumx2, sum
begin
npt = PDM_NPT(pdmp)
# Calculate the sum of squares and the variance of the data.
sumx2 = 0.0
sum = 0.0
j = 0
do i = 1, npt {
if (PDM_INUSE(pdmp,i) == 1) {
sumx2 = sumx2 + PDM_DY(pdmp,i)**2 # Sum of squares.
sum = sum + PDM_DY(pdmp,i)
j = j + 1
}
}
if (j != 1)
var = (sumx2 - sum**2/double(j))/double(j - 1) # Variance.
# Put these two values in the data structure.
PDM_SUMSQ(pdmp) = sumx2
PDM_DVAR(pdmp) = var
end
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