In my various R - Tests I'm using usually the Yahoo Dataservice implemented in quantmod
 
suppressWarnings(try(getSymbols(ticker, index.class="POSIXct", from=initDate, to=to,src="yahoo"),silent=TRUE)) 
 
If you would like to run some backtests on the DAX,MDAX or SDAX and you were wondering what the yahoo symbol is, here is a list of the tickers you need. 
 
 
"ARL.DE"  "BNR.DE"  "BOSS.DE" "BYW6.DE" "CLS1.DE" "DEQ.DE"  "DUE.DE"  "DWNI.DE" "EAD.DE" "FIE.DE"  "FPE3.DE" "FRA.DE"  "G1A.DE"  "GBF.DE"  "GFJ.DE"  "GIB.DE"  "GIL.DE"  "GWI1.DE" "GXI.DE"  "HDD.DE"  "HHFA.DE" "HNR1.DE" "HOT.DE"  "KCO.DE"  "KD8.DE"  "KRN.DE"  "KU2.DE" "LEO.DE"  "MAN.DE"  "MEO.DE"  "MTX.DE"  "NDA.DE"  "PSM.DE"  "PUM.DE"  "RAA.DE"  "RHK.DE""RHM.DE"  "SAZ.DE"  "SGL.DE"  "SKYD.DE" "SPR.DE"  "SY1.DE"  "SZG.DE"  "SZU.DE"  "TEG.DE""TLX.DE"  "TUI1.DE" "VOS.DE"  "WCH.DE"  "WIN.DE"  "ADV.DE"  "AFX.DE"  "AIXA.DE" "BBZA.DE""BC8.DE"  "COK.DE"  "DLG.DE"  "DRI.DE"  "DRW3.DE" "EUCA.DE" "EVT.DE"  "FNTN.DE" "JEN.DE""KBC.DE"  "LPK.DE"  "MOR.DE"  "NDX1.DE" "O1BC.DE" "PFV.DE"  "PSAN.DE" "QCE.F" "QIA.DE"  "QSC.DE"  "S92.DE"  "SBS.DE"  "SMHN.DE" "SOW.DE"  "SRT3.DE" "SWV.DE"  "UTDI.DE" "WDI.DE"  "2HR.DE"  "AAD.DE"  "AB1.DE"  "AOX.DE"  "B5A.DE"  "BAF.DE"  "BDT.DE"  "BIO3.DE" "CEV.DE" "COM.DE"  "CWC.DE"  "DAZ.DE"  "DBA.DE"  "DEX.DE"  "DEZ.DE"  "DUE.DE"  "EV4.DE"  "EVD.DE" "GFK.DE"  "GLJ.DE"  "GMM.DE"  "GSC1.DE" "HAB.DE"  "HAW.DE"  "HBH3.DE" "HDD.DE"  "HLG.DE" "INH.DE"  "IVG.DE"  "JUN3.DE" "KWS.DE"  "MLP.DE"  "MVV1.DE" "NOEJ.DE" "O2C.DE"  "P1Z.DE" "PMO.DE"  "PRA.DE"  "S4A.DE"  "SAX.DE"  "SFQ.DE"  "SIX2.DE" "SK1A.DE" "SKB.DE"  "SLT.DE" "TIM.DE"  "TTI.DE"  "TTK.DE"  "VT9.DE"  "WAC.DE"  "ADS.DE"  "ALV.DE"  "BAS.DE"  "BAYN.DE""BEI.DE"  "BMW.DE"  "CBK.DE"  "CON.DE"  "DAI.DE"  "DB1.DE"  "DBK.DE"  "DPW.DE" "DTE.DE" 
"EOAN.DE" "FME.DE"  "FRE.DE"  "HEI.DE"  "HEN3.DE" "IFX.DE"  "LHA.DE"  "LIN.DE"  "LXS.DE"  "MRK.DE"  "MUV2.DE" "RWE.DE"  "SAP.DE"  "SDF.DE"  "SIE.DE"  "TKA.DE"  "VOW3.DE"