Re: Lists and Loops

*To*: mathgroup at smc.vnet.net*Subject*: [mg113025] Re: Lists and Loops*From*: Albert Retey <awnl at gmx-topmail.de>*Date*: Mon, 11 Oct 2010 05:17:45 -0400 (EDT)*References*: <i8s5e7$935$1@smc.vnet.net>

Am 10.10.2010 12:44, schrieb Michaell Taylor: > I am new to Mathematica and am probably too stuck in other languages, but > but having a hard time with a simple listing building looping structure. > The code below is supposed to cycle through a list of stock tickers. For > each ticker it builds a list of certain financial data elements and adds > each element to a list. When the list is complete (all financial elements > obtained), the list is written to a Mysql database. The internal looping > structure seems to work fine. That is, if I execute the internal loop for a > single ticker, the results are added to the database as planned. > > However, the outer structure causes a problem in that the list continues to > grow with each ticker. The "mydata={}" line was meant to "reset" the list, > but doesn't seem to be performing as expected. > > tickers = {"VNO", "AMB"} > > fprop = {"Average50Day", "Average200Day"} > > Do[ > mydata = {t} > Do[ > mydata = Append[mydata, FinancialData[t, i]], > {i, fprop}] > Print[mydata] > SQLInsert[connt, "reit" , {"ticker", "first", "second"}, mydata] > {t, tickers}] > > > My error, no doubt is obvious to some. Any guidance would be greatly > appreciated. I think you are just missing some ; and , at the right places, I have not tested it but this might work: Do[ mydata = {t}; Do[mydata = Append[mydata, FinancialData[t, i]], {i, fprop}]; Print[mydata]; SQLInsert[connt, "reit", {"ticker", "first", "second"}, mydata], {t,tickers} ] Using Do loops and Append is often neither elegant nor efficient in Mathematica, something like this would probably be more Mathematica-ish: mydata = Map[ Function[{t}, Flatten[{t, FinancialData[t, #] & /@ fprop}]], tickers ]; SQLInsert[connt, "reit", {"ticker", "first", "second"}, mydata] Depending on what you try to achieve it also might be more efficient to insert all your data in one go as I did than to use a single SQLInsert for each ticker. hth, albert