[R] combining unequal dataframes based on a common grouping factor

[Brock Huntsman]

I apologize if this is a relatively easy problem, but have been stuck on
this issue for a few days. I am attempting to combine values from 2
separate dataframes. Each dataframe contains a shared identifier (GROUP).
Dataframe 1 (3272 rows x 3 columns) further divides this shared grouping
factor into unique identifiers (ID), as well as contains the proportion of
the GROUP area of which the unique identifier consists (PROP_AREA).
Dataframe 2 (291 x 14976) in addition to consisting of the shared
identifier, also has numerous columns consisting of values (VALUE1,
VALUE2). I would like to multiply the PROP_AREA in dataframe 1 by each
value in dataframe 2 (VALUE1 through VALUE14976) based on the GROUP factor,
constructing a final dataframe of size 3272 x 14976. An example of the data
frames are as follows:


frame1:

ID

GROUP

PROP_AREA

1

A

0.33

2

A

0.33

3

A

0.33

4

B

0.50

5

B

0.50

6

C

1.00

7

D

1.00



frame2:

GROUP

VALUE1

VALUE2

A

10

5

B

20

10

C

30

15

D

40

20



 Desired dataframe

frame3:

ID

VALUE1

VALUE2

1

3.3

1.65

2

3.3

1.65

3

3.3

1.65

4

10

5

5

10

5

6

30

15

7

40

20





I assume I would need to use the %in% function or if statements, but am
unsure how to write the code. I have attempted to construct a for loop with
an if statement, but have not been successful as of yet.


for(i in 1:nrow(frame1)) {

  for(j in 2:ncol(frame2)) {

    if (frame1$GROUP[i] == frame2$GROUP[i]) {

      frame3[i,j+1] <- frame1$PROP_AREA[i]*frame2[i,j+1]

    }

  }

}


Any advice on suggested code or packages to read up on would be much
appreciated.

Brock

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