[R] Problem merging two data frames

[jim holtman]

FAQ 7.31 is probably the answer.  If you want to try it, convert all
your numerics that you want to merge on to character and round to the
same value so you can "see" what is actually being matched.  Comparing
numerics for equality can present some challanges.

On Wed, Aug 26, 2009 at 9:22 PM, Mehdi Khan<mwkhan at ucdavis.edu> wrote:
> Note: even if I say by=c("LON", "LAT"), it doesn't work, suggesting that
> number storage isn't the problem
>
> On Wed, Aug 26, 2009 at 6:19 PM, Mehdi Khan <mwkhan at ucdavis.edu> wrote:
>
>> Hello everyone,
>>
>> Merging two dataframes should be easy.  However when I try to merge, R
>> doesn't recognize identical values, even if I am doing it by values that
>> have no decimals.
>>
>> willclayong:
>>    vs30      LON     LAT  Net  X wills.cat wills.vs30 clahan.cat clahanvs30
>> PolyID.wills PolyID.clahan tif.cat STA ELEVATION tif.vs30
>> 1 338.539 -3849590 4319319 <NA>  2         D        301          D
>> 377         1958          1942       1 150        NA      519
>> 2 712.822 -3849590 4319319 <NA>  3         D        301          D
>> 377         1958          1942       1 479        NA      519
>> 3 477.652 -3836584 4288164 <NA> 10         C        464          C
>> 489         1194          9353       3 148        NA      547
>> 4 513.703 -3836575 4287739 <NA> 11         C        464          C
>> 489         1194          9353       3 485        NA      547
>> 5 477.652 -3835886 4289120 <NA> 12         C        464          C
>> 489         1194          9353       7 147        NA      388
>>
>> wald:
>>
>> > wald_ol_sta[1:10,]
>>     X Wald.vs30  STA    vs30      LON     LAT
>> 1   1   434.417 1502 274.500 -3077929 3759564
>> 2   2   378.049 NEE2 363.000 -3086165 3718184
>> 3   3   196.848  EMS 336.000 -3143337 3500449
>> 4   4   557.625 1498 659.600 -3103738 3871531
>> 5   5   263.878 1497 274.500 -3102944 3878068
>> 6   6   374.898 1499 274.500 -3109753 3858460
>> 7   7   150.000  230 274.500 -3154048 3482703
>> 8   8   248.342 1205 207.469 -3153294 3497116
>> 9   9   422.256 1495 338.600 -3097854 3990339
>> 10 10   322.540 1496 274.500 -3115300 3863905
>>
>> willsclayongwald<-merge(wald_ol_sta, willsclayong, by=c("LON", "LAT",
>> "STA", "vs30"))
>>
>> returns nothing... if I modify the previous script by adding "all=TRUE", I
>> get this:
>>
>>
>> lsclayongwald[1:10,]
>>         LON     LAT STA    vs30  X.x       Wald.vs30  Net X.y wills.cat
>> wills.vs30 clahan.cat clahanvs30 PolyID.wills PolyID.clahan tif.cat
>> ELEVATION tif.vs30
>> 1  -3854850 4321856 478  513.703 1155       586.685 <NA>  NA
>> <NA>         NA       <NA>         NA           NA            NA
>> NA        NA       NA
>> 2  -3849590 4319319 150  338.539   NA         NA <NA>   2         D
>> 301          D        377         1958          1942       1        NA
>> 519
>> 3  -3849590 4319319 479  712.822   NA         NA <NA>   3         D
>> 301          D        377         1958          1942       1        NA
>> 519
>> 4  -3849590 4319319 150  338.539 1152       336.794 <NA>  NA
>> <NA>         NA       <NA>         NA           NA            NA
>> NA        NA       NA
>>
>>
>> rows 2 and 4 should have merged.  Why didn't they?
>>
>>
>> thanks!
>>
>>
>> Mehdi Khan
>>
>>
>
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-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem that you are trying to solve?