Excel like column operations in R dataframe

dataframe, r

Solution

My brain is doing this under protest. It makes me feel that I'm back at a Minitab session.

 dfrm$C <- NA
 dfrm$C[5:10] <- with(dfrm, (B[5:10]-B[1:6])*A[5:10])
 dfrm$D <- NA
 dfrm$D[5:10] <- cumsum(dfrm$C[5:10])
 dfrm$E <- NA
 dfrm$E[5:10] <- 1 - 2*(dfrm$D[5:10] <= 100) # could also use ifelse()

dfrm
       A     B       C       D  E
1  100.5 101.3      NA      NA NA
2  102.6 102.5      NA      NA NA
3  107.2 109.3      NA      NA NA
4   99.3  89.3      NA      NA NA
5  102.8 100.7  -61.68  -61.68 -1
6  107.2  98.9 -385.92 -447.60 -1
7   99.8 109.9   59.88 -387.72 -1
8  108.2  99.5 1103.64  715.92  1
9   78.7  89.6 -873.57 -157.65 -1
10 108.9 109.2 1121.67  964.02  1

Problem

I am trying to replicate some modelling I did in Excel, using R. I have read the data from a csv file into a dataframe. The csv file contains two columns of data A and B. I now want to add additional columns C, D and E to the dataframe and to populate the new columns C, D and E with data generated by applying a formula to the data in the previous columns. The snippet below should hopefully clarify what I'm trying to do: ``` A B C D E 1 100.5 101.3 2 102.6 102.5 3 107.2 109.3 4 99.3 89.3 5 102.8 100.7 =(B5-B1)*A5 = C5 = IF(D5 >100,1,-1) 6 107.2 98.9 =(B6-B2)*A6 = C6+C5 = IF(D6 >100,1,-1) 7 99.8 109.9 =(B7-B3)*A7 = C7+C6 = IF(D7 >100,1,-1) 8 108.2 99.5 =(B8-B4)*A8 = C8+C7 = IF(D8 >100,1,-1) 9 78.7 89.6 =(B9-B5)*A9 = C9+C8 = IF(D9 >100,1,-1) 10 108.9 109.2 =(B10-B6)*A10 = C10+C9 = IF(D10 >100,1,-1) ``` How can I replicate this kind of "columnar" functional programming that Excel (ahem - Excels) in - using R?

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