[R] Matching two datasets and updating values

[Petr PIKAL]

Hi
> 
> Dear R forum
> 
> I have two datafarmes with category and cat_val forming one dataframe 
and 
> cust and cust_category forming another dataframe.
> 
> category = c("C", "D", "B", "A")
> cat_val = c(0.10, 0.25, 0.40, 0.54)
> cust = c("cust_1", "cust_2", "cust_3", "cust_4", "cust_5", "cust_6", 
> "cust_7", "cust_8", "cust_9", "cust_10")
> cust_category = c("C", "A", "A", "A", "A", "C", "D", "B", "B", "D")
> 
> Thus, I have 
> 
> > category
> [1] "C" "D" "B" "A"
> 
> > cat_val
> [1] 0.10 0.25 0.40 0.54
> 
> > cust
>  [1] "cust_1"  "cust_2"  "cust_3"  "cust_4"  "cust_5" 
>  [6] "cust_6"  "cust_7"  "cust_8"  "cust_9"  "cust_10"
> 
> > cust_category
>  [1] "C" "A" "A" "A" "A" "C" "D" "B" "B" "D"
> 
> My problem is to match 'cust_category' with 'category' and accordingly 
> selct the value assigned to this category value. In other words, 1st 
> element of cust_category is "C", so it should select the value 0.10, the 

> second element is "A", so it should assign value 0.54 against this. So 
> effectively I should get

What about merge?

a<-data.frame(category, cat_val)
b<-data.frame(cust, cust_category)
merge(a,b, by.x="category", by.y="cust_category")
   category cat_val    cust
1         A    0.54  cust_3
2         A    0.54  cust_4
3         A    0.54  cust_5
4         A    0.54  cust_2
5         B    0.40  cust_8
6         B    0.40  cust_9
7         C    0.10  cust_1
8         C    0.10  cust_6
9         D    0.25  cust_7
10        D    0.25 cust_10


Regards
Petr



> 
> cust        cust_category  cat_val
> cust_1        C                   0.10  
> cust_2        A                   0.54
> cust_3        A                   0.54
> ............................................
> cust_10      D                   0.25 
> 
> 
> Kindly guide
> 
> Regards
> 
> Vincy
> 
> 
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> 
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