Hello, First of all, I really want to thank you Nicolas, for the enormous work you do on a daily basis to improve our understanding of the programming tools associated with PRT. I wanted to go back to the tapes associated with the daily VWAP on PRT. The formula "VWAP = SUMMATION [d] (volume * typicalprice) / SUMMATION [d] (volume)" is correct. There is no doubt about it. On the other hand, I programmed the different standard deviations with the formula "sd = std [d] (abs (typicalprice-VWAP))" and I obtain results which absolutely do not match those of PRT. I suggest you see this difference in the attachment. Thanks for your feedback