FUNCTION Weightm, data, sig, flag
good_values = where(flag gt 0, good_num)
if good_num gt 0 then begin
data_short = data[good_values]
sig_short = sig[good_values]
wts = 1.0 / (sig_short)^2
sum = total(wts*data_short)
n = total(wts)
mean = sum / n
sdm = sqrt(total((sig_short)^2)) / sqrt(good_num)
meansdm = [mean, sdm, good_num]
endif else if good_num eq 0 then begin
meansdm = [-1, -1, 0]
endif
RETURN, meansdm
END