Creating Conditional Columns in R

I've to create two columns (OPop and WPop) in the following dataframe Data:

OState  OCounty WState  WCounty OYear
AL  Autauga AL  Baldwin 2004
AL  Barbour AL  Bibb    2001
CA  Amador  WY  Weston  1985
CA  Alameda CA  Amador  1999

The values of OPop and WPop are based on the values of the four columns (Pop1980, Pop1990, Pop2000 and Pop2010) of another dataframe Data1

State   County  Pop1980 Pop1990 Pop2000 Pop2010
AL  Autauga 32259   34222   43671   54571
AL  Baldwin 78556   98280   140415  182265
AK  Aleutians East  7768    2464    2697    3141
AK  Aleutians West  NA  9478    5465    5561
CA  Alameda 1105379 12791开发者_StackOverflow社区82 1443741 1510271
CA  Alpine  1097    1113    1208    1175
CA  Amador  19314   30039   35100   38091
CA  Butte   143851  182120  203171  220000
WY  Uinta   13021   18705   19742   21118
WY  Washakie    9496    8388    8289    8533
WY  Weston  7106    6518    6644    7208



Data$OPop <- ifelse(test = Data$OState == Data1$State & Data$OCounty == Data1$County &
                       Data$OYear >= 1980 & Data$OYear < 1990,
                yes = Data1$Pop1980,
                no = ifelse(test = Data$OState == Data1$State & Data$OCounty == Data1$County &
                                   Data$OYear >= 1990 & Data$OYear < 2000,
                             yes = Data1$Pop1990,
                             no = ifelse(test = Data$OState == Data1$State & Data$OCounty == Data1$County &
                                                Data$OYear >= 2000 & Data$OYear < 2010,
                                         yes = Data1$Pop2000,
                                         no = ifelse(test = Data$OState == Data1$State & Data$OCounty == Data1$County &
                                                            Data$OYear >= 2010 & Data$OYear < 2011,
                                                     yes = Data1$Pop2010,
                                                     no = NA))))

Any help will be highly appreciated. Thanks

EDIT

I got the following error message:

Error in Ops.factor(Data$OState, Data1$State) : 
  level sets of factors are different
In addition: Warning message:
In is.na(e1) | is.na(e2) :
  longer object length is not a multiple of shorter object length

I am going to show you what merge can do. If this is not what you wanted then USE NATURAL LANGUAGE rather than convoluted code) to explain what you want. "O" and "W" are not sufficient hints to determine your goal. Assume these are two data.frames: "dat1", "dat2" (from which you have removed the extraneous and length-deficient row:

    >  merge(dat2, dat1, 1:2)
  State  County Pop1980 Pop1990 Pop2000 Pop2010 WState WCounty OYear
1    AL Autauga   32259   34222   43671   54571     AL Baldwin  2004
2    CA Alameda 1105379 1279182 1443741 1510271     CA  Amador  1999
3    CA  Amador   19314   30039   35100   38091     WY  Weston  1985