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# AVGSNR -- Compute average value and signal-to-noise in region
procedure avgsnr (sh, wx1, wy1, y, n, fd1, fd2)
pointer sh
real wx1, wy1
real y[n]
int n
int fd1, fd2
char command[SZ_FNAME]
real wx2, wy2
real avg, snr, rms
int i, i1, i2, nsum
int wc, key
int clgcur()
begin
# Get second position
call printf ("m again:")
call flush (STDOUT)
i = clgcur ("cursor", wx2, wy2, wc, key, command, SZ_FNAME)
# Fix pixel indices
call fixx (sh, wx1, wx2, wy1, wy2, i1, i2)
if (i1 == i2) {
call printf ("Cannot determine SNR - move cursor")
return
}
# Compute avg, rms, snr
nsum = i2 - i1 + 1
avg = 0.
rms = 0.
snr = 0.
if (nsum > 0) {
do i = i1, i2
avg = avg + y[i]
avg = avg / nsum
}
if (nsum > 1) {
call alimr (y[i1], nsum, wy1, wy2)
wy1 = wy2 - wy1
if (wy1 > 0.) {
do i = i1, i2
rms = rms + ((y[i] - avg) / wy1) ** 2
rms = wy1 * sqrt (rms / (nsum-1))
snr = avg / rms
}
}
# Print out
call printf ("avg: %10.4g rms: %10.4g snr: %8.2f\n")
call pargr (avg)
call pargr (rms)
call pargr (snr)
if (fd1 != NULL) {
call fprintf (fd1, "avg: %10.4g rms: %10.4g snr: %8.2f\n")
call pargr (avg)
call pargr (rms)
call pargr (snr)
}
if (fd2 != NULL) {
call fprintf (fd2, "avg: %10.4g rms: %10.4g snr: %8.2f\n")
call pargr (avg)
call pargr (rms)
call pargr (snr)
}
end
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