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From |
Nadine R <tanzmaus1986@googlemail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
st: calculate gains and losses from stock prices |

Date |
Tue, 5 Jul 2011 21:58:55 +0200 |

Hello statalisters! I have a timeseries of share prices and many people buying (purchase P) and selling (sell S) shares. I want to calculate the accrued gains and losses if someone who bought the share earlier sells it after a while. My data looks like this (stata version 11.0): trading_day transaction_type person_id number of shares price gain_loss 1 1 1 2 P 1 10 1.2 0 3 1 1.4 =10*(1.4-1.2) 4 P 1 20 1.6 =20*(1.6-1.6)+10*(1.6-1.2) 5 1 1.5 =20*(1.5-1.6)+10*(1.5-1.2) 6 S 1 25 1.3 =10*(1.3-1.2)+15*(1.3-1.6) 7 1 1.5 =5*(1.5-1.6) 8 S 1 15 1.4 =5*(1.4-1.6) 9 1 1.6 10 1 1.8 11 1 1.6 12 P 1 10 1.7 =10*(1.7-1.7) 13 1 1.5 =10*(1.5-1.7) 14 S 1 5 1.3 =5*(1.3-1.7) 1 2 What I have written in the collum gain_loss is what Stata should calculate: once a share is bought, following purchases accumulate and gains/losses are calculated. If some shares are sold this happens by the FIFO-method (shares first bought are first sold). It is only possible to sell shares which were bought before (see day 8, where 15 shares are sold but only for 5 the gains/losses are calculated). On day 8 there are zero shares in the portfolio and on day 12 all starts from the beginning. If the first transaction a sell it should be ignored as no shares were bought before. This happens for a timeseries of person 1 and then for person 2 and so on... How can I let Stata calculate theses gains and losses? With a kind of loop? Thank you a lot in advance for your help. Nadine * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

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