Question about dataframe manipulations. not HW, although I will phrase it as a HW problem. I know there is a 3 line way of doing this but I can't seem to find it.
Problem
I have a dataframe A with 10 columns and a thousand rows, it's filled with some data. I have a 1-column matrix B with 1 column and a thousand rows, it's filled by 1 and 0 (TRUE or FALSE).
Goal: create a new dataframe C that contains only the rows in A that had a TRUE value in the equivalent index of matrix C.
(More clarification in case its not clear) I performed operations on A, stored the result (true or false) in a column dataframe (of same length of course) and now wish to extract that into its own matrix.
The size of the new matrix is sum(B) X 10 (just a logical deduction)
Thank you for reading! Your help is appreciated.
Example
Dataframe A
Name State metric1 metric2
Joe MA 23 25
Moe AZ 123 2971
Bo CA 938 387
Yo UT 1 3
matrix B
1
0
1
0
Desired Output (dataframe C)
Name State metric1 metric2
Joe MA 23 25
Bo CA 938 387
Why not simply
A <- data.frame(cbind(A=1:10,B=21:30,C=41:50))
B <- data.frame(D=rep(c(TRUE,FALSE),5))
C <- A[B$D,]
giving
> A
A B C
1 1 21 41
2 2 22 42
3 3 23 43
4 4 24 44
5 5 25 45
6 6 26 46
7 7 27 47
8 8 28 48
9 9 29 49
10 10 30 50
> B
D
1 TRUE
2 FALSE
3 TRUE
4 FALSE
5 TRUE
6 FALSE
7 TRUE
8 FALSE
9 TRUE
10 FALSE
> C
A B C
1 1 21 41
3 3 23 43
5 5 25 45
7 7 27 47
9 9 29 49
EDIT after OP's edit
A <- data.frame(cbind(name=c("Joe", "Moe", "Bo" , "Yo"),
State=c("MA","AZ","CA","UT"),
metric1 = c(23,123,938,1),
metric2 = c(25,2971,387,3)))
B <- c(1,0,1,0)
C <- A[B==1,]
C
giving
> C
name State metric1 metric2
1 Joe MA 23 25
3 Bo CA 938 387